diff --git a/docs/docs/documentation/getting-started/installation/backend-config.md b/docs/docs/documentation/getting-started/installation/backend-config.md
index 27dae3885..6b030c0fc 100644
--- a/docs/docs/documentation/getting-started/installation/backend-config.md
+++ b/docs/docs/documentation/getting-started/installation/backend-config.md
@@ -29,6 +29,7 @@
 | --------------------------- | :-----: | ----------------------------------------------------------------------------------- |
 | SECURITY_MAX_LOGIN_ATTEMPTS |    5    | Maximum times a user can provide an invalid password before their account is locked |
 | SECURITY_USER_LOCKOUT_TIME  |   24    | Time in hours for how long a users account is locked                                |
+| ALLOWED_IFRAME_HOSTS        |  `""`   | Comma-separated extra hostnames allowed as `<iframe>` sources in recipe content. Extends the built-in list of trusted video providers (YouTube, Vimeo). Subdomains are included automatically. Only `https` sources are permitted. Adding hosts here opts into rendering embeds from those origins to all viewers, including the public, so add only origins you trust. |
 
 ### Database
 
diff --git a/frontend/app/components/Domain/Announcement/Announcements/2026-05-31_1_iframe-embeds.vue b/frontend/app/components/Domain/Announcement/Announcements/2026-05-31_1_iframe-embeds.vue
new file mode 100644
index 000000000..5b862f7e7
--- /dev/null
+++ b/frontend/app/components/Domain/Announcement/Announcements/2026-05-31_1_iframe-embeds.vue
@@ -0,0 +1,54 @@
+<template>
+  <div>
+    <p>
+      To harden Mealie against malicious content, <code>&lt;iframe&gt;</code> embeds in recipe
+      instructions, notes, and descriptions are now restricted to a trusted set of hosts.
+    </p>
+    <div class="mb-2">
+      By default, embeds are allowed only from well-known video providers:
+      <ul class="ml-6">
+        <li>YouTube</li>
+        <li>Vimeo</li>
+      </ul>
+    </div>
+    <p>
+      Existing recipes that embed content from <strong>other</strong> hosts will no longer render
+      those embeds. The rest of the recipe is unaffected.
+    </p>
+    <div v-if="user?.admin">
+      <hr class="mt-2 mb-4">
+      <p>
+        As an admin, you can allow additional hosts with the <code>ALLOWED_IFRAME_HOSTS</code>
+        environment variable (comma-separated). It extends the built-in defaults, and only
+        <code>https</code> sources are permitted. See the configuration docs for details:
+        <br>
+        <v-btn
+          class="mt-2"
+          color="primary"
+          href="https://docs.mealie.io/documentation/getting-started/installation/backend-config/"
+          target="_blank"
+        >
+          Backend Configuration
+        </v-btn>
+      </p>
+    </div>
+  </div>
+</template>
+
+<script setup lang="ts">
+import type { AnnouncementMeta } from "~/composables/use-announcements";
+
+const { user } = useMealieAuth();
+</script>
+
+<script lang="ts">
+export const meta: AnnouncementMeta = {
+  title: "Recipe embeds restricted to trusted hosts",
+};
+</script>
+
+<style scoped lang="css">
+p {
+  padding-bottom: 8px;
+}
+</style>
diff --git a/frontend/app/components/Domain/Recipe/RecipeChips.vue b/frontend/app/components/Domain/Recipe/RecipeChips.vue
index fc23c4338..e28db7c36 100644
--- a/frontend/app/components/Domain/Recipe/RecipeChips.vue
+++ b/frontend/app/components/Domain/Recipe/RecipeChips.vue
@@ -25,6 +25,7 @@
 
 <script setup lang="ts">
 import type { RecipeCategory, RecipeTag, RecipeTool } from "~/lib/api/types/recipe";
+import { truncateText as truncatePlainText } from "~/lib/sanitize/text";
 
 export type UrlPrefixParam = "tags" | "categories" | "tools";
 
@@ -50,10 +51,7 @@ const props = withDefaults(defineProps<Props>(), {
 defineEmits(["item-selected"]);
 function truncateText(text: string, length = 20, clamp = "...") {
   if (!props.truncate) return text;
-  const node = document.createElement("div");
-  node.innerHTML = text;
-  const content = node.textContent || "";
-  return content.length > length ? content.slice(0, length) + clamp : content;
+  return truncatePlainText(text, length, clamp);
 }
 </script>
 
diff --git a/frontend/app/components/global/SafeMarkdown.vue b/frontend/app/components/global/SafeMarkdown.vue
index bb41ff9ad..84056952e 100644
--- a/frontend/app/components/global/SafeMarkdown.vue
+++ b/frontend/app/components/global/SafeMarkdown.vue
@@ -4,12 +4,8 @@
 </template>
 
 <script setup lang="ts">
-import DOMPurify from "isomorphic-dompurify";
 import { marked } from "marked";
-
-enum DOMPurifyHook {
-  UponSanitizeAttribute = "uponSanitizeAttribute",
-}
+import { sanitizeMarkdownHtml } from "~/lib/sanitize/markdown";
 
 const props = defineProps({
   source: {
@@ -18,48 +14,11 @@ const props = defineProps({
   },
 });
 
-const ALLOWED_STYLE_TAGS = [
-  "background-color", "color", "font-style", "font-weight", "text-decoration", "text-align",
-];
-
-function sanitizeMarkdown(rawHtml: string | null | undefined): string {
-  if (!rawHtml) {
-    return "";
-  }
-
-  DOMPurify.addHook(DOMPurifyHook.UponSanitizeAttribute, (node, data) => {
-    if (data.attrName === "style") {
-      const styles = data.attrValue.split(";").filter((style) => {
-        const [property] = style.split(":");
-        return ALLOWED_STYLE_TAGS.includes(property.trim().toLowerCase());
-      });
-      data.attrValue = styles.join(";");
-    }
-  });
-
-  const sanitized = DOMPurify.sanitize(rawHtml, {
-    ALLOWED_TAGS: [
-      "strong", "em", "b", "i", "u", "p", "code", "pre", "samp", "kbd", "var", "sub", "sup", "dfn", "cite",
-      "small", "address", "hr", "br", "id", "div", "span", "h1", "h2", "h3", "h4", "h5", "h6",
-      "ul", "ol", "li", "dl", "dt", "dd", "abbr", "a", "img", "blockquote", "iframe",
-      "del", "ins", "table", "thead", "tbody", "tfoot", "tr", "th", "td", "colgroup",
-    ],
-    ALLOWED_ATTR: [
-      "href", "src", "alt", "height", "width", "class", "allow", "title", "allowfullscreen", "frameborder",
-      "scrolling", "cite", "datetime", "name", "abbr", "target", "border", "start", "style",
-    ],
-  });
-
-  Object.values(DOMPurifyHook).forEach((hook) => {
-    DOMPurify.removeHook(hook);
-  });
-
-  return sanitized;
-}
+const { $appInfo } = useNuxtApp();
 
 const value = computed(() => {
   const rawHtml = marked.parse(props.source || "", { async: false, breaks: true });
-  return sanitizeMarkdown(rawHtml);
+  return sanitizeMarkdownHtml(rawHtml, $appInfo?.allowedIframeHosts ?? []);
 });
 </script>
 
diff --git a/frontend/app/lib/api/types/admin.ts b/frontend/app/lib/api/types/admin.ts
index 173fa8a74..7a086e07f 100644
--- a/frontend/app/lib/api/types/admin.ts
+++ b/frontend/app/lib/api/types/admin.ts
@@ -48,6 +48,7 @@ export interface AppInfo {
   oidcRedirect: boolean;
   oidcProviderName: string;
   tokenTime: number;
+  allowedIframeHosts?: string[];
 }
 export interface AppStartupInfo {
   isFirstLogin: boolean;
diff --git a/frontend/app/lib/sanitize/markdown.test.ts b/frontend/app/lib/sanitize/markdown.test.ts
new file mode 100644
index 000000000..b1d0e4cdb
--- /dev/null
+++ b/frontend/app/lib/sanitize/markdown.test.ts
@@ -0,0 +1,74 @@
+import { describe, expect, test } from "vitest";
+import { sanitizeMarkdownHtml } from "./markdown";
+
+describe("sanitizeMarkdownHtml", () => {
+  test("returns empty string for nullish input", () => {
+    expect(sanitizeMarkdownHtml(null)).toEqual("");
+    expect(sanitizeMarkdownHtml(undefined)).toEqual("");
+    expect(sanitizeMarkdownHtml("")).toEqual("");
+  });
+
+  test("keeps allowed formatting tags", () => {
+    const html = sanitizeMarkdownHtml("<p>Mix <strong>flour</strong> and <em>water</em></p>");
+    expect(html).toContain("<strong>flour</strong>");
+    expect(html).toContain("<em>water</em>");
+  });
+
+  test("strips script tags and event handlers", () => {
+    const html = sanitizeMarkdownHtml("<p onclick=\"alert(1)\">hi</p><script>alert(1)</script>");
+    expect(html).not.toContain("script");
+    expect(html).not.toContain("onclick");
+    expect(html).not.toContain("alert");
+  });
+
+  test("strips img onerror payloads", () => {
+    const html = sanitizeMarkdownHtml("<img src=x onerror=alert(1)>");
+    expect(html).not.toContain("onerror");
+  });
+
+  // Form controls must never render in user content.
+  test("strips form, input, and button elements", () => {
+    const html = sanitizeMarkdownHtml("<form action=/x><input name=p><button>go</button></form>");
+    expect(html).not.toContain("<form");
+    expect(html).not.toContain("<input");
+    expect(html).not.toContain("<button");
+  });
+
+  test("strips iframes when no allowed hosts are configured", () => {
+    const html = sanitizeMarkdownHtml("<iframe src=\"https://evil.example/x\"></iframe>", []);
+    expect(html).not.toContain("<iframe");
+  });
+
+  test("strips iframes whose src host is not allowlisted", () => {
+    const html = sanitizeMarkdownHtml(
+      "<iframe src=\"https://evil.example/x\"></iframe>",
+      ["youtube.com"],
+    );
+    expect(html).not.toContain("<iframe");
+  });
+
+  test("strips non-https iframes even for an allowlisted host", () => {
+    const html = sanitizeMarkdownHtml(
+      "<iframe src=\"http://www.youtube.com/embed/abc\"></iframe>",
+      ["youtube.com"],
+    );
+    expect(html).not.toContain("<iframe");
+  });
+
+  test("keeps iframes from an allowlisted host (incl. subdomains)", () => {
+    const html = sanitizeMarkdownHtml(
+      "<iframe src=\"https://www.youtube.com/embed/abc\"></iframe>",
+      ["youtube.com"],
+    );
+    expect(html).toContain("<iframe");
+    expect(html).toContain("https://www.youtube.com/embed/abc");
+  });
+
+  test("does not allow a lookalike host to pass the suffix check", () => {
+    const html = sanitizeMarkdownHtml(
+      "<iframe src=\"https://notyoutube.com/embed/abc\"></iframe>",
+      ["youtube.com"],
+    );
+    expect(html).not.toContain("<iframe");
+  });
+});
diff --git a/frontend/app/lib/sanitize/markdown.ts b/frontend/app/lib/sanitize/markdown.ts
new file mode 100644
index 000000000..5cddae720
--- /dev/null
+++ b/frontend/app/lib/sanitize/markdown.ts
@@ -0,0 +1,98 @@
+import DOMPurify from "isomorphic-dompurify";
+
+enum DOMPurifyHook {
+  UponSanitizeAttribute = "uponSanitizeAttribute",
+  AfterSanitizeAttributes = "afterSanitizeAttributes",
+}
+
+const ALLOWED_STYLE_PROPERTIES = [
+  "background-color", "color", "font-style", "font-weight", "text-decoration", "text-align",
+];
+
+const BASE_ALLOWED_TAGS = [
+  "strong", "em", "b", "i", "u", "p", "code", "pre", "samp", "kbd", "var", "sub", "sup", "dfn", "cite",
+  "small", "address", "hr", "br", "id", "div", "span", "h1", "h2", "h3", "h4", "h5", "h6",
+  "ul", "ol", "li", "dl", "dt", "dd", "abbr", "a", "img", "blockquote",
+  "del", "ins", "table", "thead", "tbody", "tfoot", "tr", "th", "td", "colgroup",
+];
+
+const BASE_ALLOWED_ATTR = [
+  "href", "src", "alt", "height", "width", "class", "title",
+  "cite", "datetime", "name", "abbr", "target", "border", "start", "style",
+];
+
+// Attributes only meaningful on an <iframe>; added to the allowlist solely when iframe embeds
+// are enabled via a configured host allowlist.
+const IFRAME_ALLOWED_ATTR = ["allow", "allowfullscreen", "frameborder", "scrolling"];
+
+/**
+ * Returns true if an iframe `src` points at one of the allowed hosts. Only https URLs are
+ * accepted, and a configured host matches the URL's hostname exactly or as a parent domain
+ * (e.g. "youtube.com" matches "www.youtube.com").
+ */
+function isAllowedIframeSrc(src: string, allowedHosts: string[]): boolean {
+  let url: URL;
+  try {
+    url = new URL(src);
+  }
+  catch {
+    return false;
+  }
+
+  if (url.protocol !== "https:") {
+    return false;
+  }
+
+  const hostname = url.hostname.toLowerCase();
+  return allowedHosts.some((host) => {
+    const allowed = host.toLowerCase();
+    return hostname === allowed || hostname.endsWith(`.${allowed}`);
+  });
+}
+
+/**
+ * Sanitizes pre-rendered HTML (from markdown) for display in user content such as recipe
+ * instructions, notes, and descriptions.
+ *
+ * Only the tags in `BASE_ALLOWED_TAGS` and attributes in `BASE_ALLOWED_ATTR` survive; everything
+ * else (scripts, event handlers, form controls, ...) is dropped. `style` attributes are filtered
+ * down to the properties in `ALLOWED_STYLE_PROPERTIES`. `<iframe>` is only kept when
+ * `allowedIframeHosts` is non-empty, and even then any iframe whose `src` is not an https URL on
+ * the host allowlist is removed.
+ */
+export function sanitizeMarkdownHtml(rawHtml: string | null | undefined, allowedIframeHosts: string[] = []): string {
+  if (!rawHtml) {
+    return "";
+  }
+
+  const allowIframe = allowedIframeHosts.length > 0;
+
+  DOMPurify.addHook(DOMPurifyHook.UponSanitizeAttribute, (_node, data) => {
+    if (data.attrName === "style") {
+      const styles = data.attrValue.split(";").filter((style) => {
+        const [property] = style.split(":");
+        return ALLOWED_STYLE_PROPERTIES.includes(property.trim().toLowerCase());
+      });
+      data.attrValue = styles.join(";");
+    }
+  });
+
+  if (allowIframe) {
+    DOMPurify.addHook(DOMPurifyHook.AfterSanitizeAttributes, (node) => {
+      if (node.nodeName === "IFRAME" && !isAllowedIframeSrc(node.getAttribute("src") || "", allowedIframeHosts)) {
+        node.parentNode?.removeChild(node);
+      }
+    });
+  }
+
+  const sanitized = DOMPurify.sanitize(rawHtml, {
+    ALLOWED_TAGS: allowIframe ? [...BASE_ALLOWED_TAGS, "iframe"] : BASE_ALLOWED_TAGS,
+    ALLOWED_ATTR: allowIframe ? [...BASE_ALLOWED_ATTR, ...IFRAME_ALLOWED_ATTR] : BASE_ALLOWED_ATTR,
+  });
+
+  Object.values(DOMPurifyHook).forEach((hook) => {
+    DOMPurify.removeHook(hook);
+  });
+
+  return sanitized;
+}
diff --git a/frontend/app/lib/sanitize/text.test.ts b/frontend/app/lib/sanitize/text.test.ts
new file mode 100644
index 000000000..6ad9f1315
--- /dev/null
+++ b/frontend/app/lib/sanitize/text.test.ts
@@ -0,0 +1,35 @@
+import { describe, expect, test, vi } from "vitest";
+import { truncateText } from "./text";
+
+describe("truncateText", () => {
+  test("returns short text unchanged", () => {
+    expect(truncateText("Dinner")).toEqual("Dinner");
+  });
+
+  test("truncates long text with clamp", () => {
+    expect(truncateText("a".repeat(25))).toEqual(`${"a".repeat(20)}...`);
+  });
+
+  test("respects custom length and clamp", () => {
+    expect(truncateText("abcdef", 3, "~")).toEqual("abc~");
+  });
+
+  test("does not clamp text exactly at the length boundary", () => {
+    expect(truncateText("abcde", 5)).toEqual("abcde");
+    expect(truncateText("abcdef", 5)).toEqual("abcde...");
+  });
+
+  // Markup in the input must be treated as plain text and never parsed into the live document.
+  test("does not parse or execute HTML payloads", () => {
+    const createElement = vi.spyOn(document, "createElement");
+    const payload = "<img src=x onerror=alert(1)>";
+
+    const result = truncateText(payload);
+
+    // The payload is returned verbatim (truncated only by length), proving it is treated as text.
+    expect(result).toEqual(`${payload.slice(0, 20)}...`);
+    // No DOM element is constructed, so no <img> can fire its onerror handler.
+    expect(createElement).not.toHaveBeenCalled();
+    createElement.mockRestore();
+  });
+});
diff --git a/frontend/app/lib/sanitize/text.ts b/frontend/app/lib/sanitize/text.ts
new file mode 100644
index 000000000..a4c56bc5a
--- /dev/null
+++ b/frontend/app/lib/sanitize/text.ts
@@ -0,0 +1,9 @@
+/**
+ * Truncates plain text to `length` characters, appending `clamp` when truncated.
+ *
+ * The input is treated strictly as text and is never parsed as HTML, so markup in the input is
+ * returned verbatim rather than interpreted.
+ */
+export function truncateText(text: string, length = 20, clamp = "..."): string {
+  return text.length > length ? text.slice(0, length) + clamp : text;
+}
diff --git a/mealie/core/settings/settings.py b/mealie/core/settings/settings.py
index 36335e014..474b61648 100644
--- a/mealie/core/settings/settings.py
+++ b/mealie/core/settings/settings.py
@@ -33,6 +33,16 @@ class FeatureDetails(NamedTuple):
         return s
 
 
+DEFAULT_ALLOWED_IFRAME_HOSTS = [
+    "youtube.com",
+    "youtube-nocookie.com",
+    "vimeo.com",
+    "player.vimeo.com",
+]
+"""Secure-by-default hostnames permitted as `<iframe>` sources in user content. Limited to
+well-known video providers. Subdomains of these hosts are also allowed (e.g. `www.youtube.com`)."""
+
+
 MaskedNoneString = Annotated[
     str | None,
     PlainSerializer(lambda x: None if x is None else "*****", return_type=str | None),
@@ -150,6 +160,19 @@ class AppSettings(AppLoggingSettings):
     ALLOW_SIGNUP: bool = False
     ALLOW_PASSWORD_LOGIN: bool = True
 
+    ALLOWED_IFRAME_HOSTS: str = ""
+    """Comma-separated list of additional hostnames allowed as `<iframe>` sources in user content
+    (recipe instructions, notes, descriptions). Extends `DEFAULT_ALLOWED_IFRAME_HOSTS`. Subdomains of
+    a listed host are also allowed. Adding hosts is opt-in to riskier behavior; the defaults are
+    limited to well-known video providers."""
+
+    @property
+    def allowed_iframe_hosts(self) -> list[str]:
+        """The full set of hostnames permitted as `<iframe>` sources, secure defaults plus any
+        admin-configured additions via `ALLOWED_IFRAME_HOSTS`."""
+        extra = [host.strip().lower() for host in self.ALLOWED_IFRAME_HOSTS.split(",") if host.strip()]
+        return list(dict.fromkeys(DEFAULT_ALLOWED_IFRAME_HOSTS + extra))
+
     DAILY_SCHEDULE_TIME: str = "23:45"
     """Local server time, in HH:MM format. See `DAILY_SCHEDULE_TIME_UTC` for the parsed UTC equivalent"""
 
diff --git a/mealie/routes/app/app_about.py b/mealie/routes/app/app_about.py
index 8012358f9..d08abdc47 100644
--- a/mealie/routes/app/app_about.py
+++ b/mealie/routes/app/app_about.py
@@ -43,6 +43,7 @@ def get_app_info(session: Session = Depends(generate_session)):
         oidc_provider_name=settings.OIDC_PROVIDER_NAME,
         allow_password_login=settings.ALLOW_PASSWORD_LOGIN,
         token_time=settings.TOKEN_TIME,
+        allowed_iframe_hosts=settings.allowed_iframe_hosts,
     )
 
 
diff --git a/mealie/routes/media/media_recipe.py b/mealie/routes/media/media_recipe.py
index 428fac95c..d0282bb1e 100644
--- a/mealie/routes/media/media_recipe.py
+++ b/mealie/routes/media/media_recipe.py
@@ -58,6 +58,13 @@ async def get_recipe_asset(recipe_id: UUID4, file_name: str):
         raise HTTPException(status.HTTP_400_BAD_REQUEST)
 
     if file.exists():
-        return FileResponse(file, filename=file.name, content_disposition_type="attachment")
+        # Force download and disable MIME sniffing so uploaded assets cannot be
+        # served as active content in Mealie's origin.
+        return FileResponse(
+            file,
+            filename=file.name,
+            content_disposition_type="attachment",
+            headers={"X-Content-Type-Options": "nosniff"},
+        )
     else:
         raise HTTPException(status.HTTP_404_NOT_FOUND)
diff --git a/mealie/schema/admin/about.py b/mealie/schema/admin/about.py
index 002461100..51f71a847 100644
--- a/mealie/schema/admin/about.py
+++ b/mealie/schema/admin/about.py
@@ -22,6 +22,7 @@ class AppInfo(MealieModel):
     oidc_redirect: bool
     oidc_provider_name: str
     token_time: int
+    allowed_iframe_hosts: list[str] = []
 
 
 class AppTheme(MealieModel):
diff --git a/tests/integration_tests/user_recipe_tests/test_recipe_image_assets.py b/tests/integration_tests/user_recipe_tests/test_recipe_image_assets.py
index 599edc624..d0cee8d21 100644
--- a/tests/integration_tests/user_recipe_tests/test_recipe_image_assets.py
+++ b/tests/integration_tests/user_recipe_tests/test_recipe_image_assets.py
@@ -104,6 +104,33 @@ def test_recipe_asset_dangerous_extension_blocked(
         assert response.status_code == 400, f"expected 400 for extension={ext}, got {response.status_code}"
 
 
+def test_recipe_asset_served_as_attachment(
+    api_client: TestClient, unique_user: TestUser, recipe_ingredient_only: Recipe
+):
+    """Assets must be served as downloads with MIME sniffing disabled so uploaded files cannot
+    execute as active content in Mealie's origin."""
+    recipe = recipe_ingredient_only
+    payload = {"name": random_string(10), "icon": "mdi-file", "extension": "txt"}
+    file_payload = {"file": b"<script>alert(1)</script>"}
+
+    response = api_client.post(
+        f"/api/recipes/{recipe.slug}/assets",
+        data=payload,
+        files=file_payload,
+        headers=unique_user.token,
+    )
+    assert response.status_code == 200
+
+    recipe_response = api_client.get(f"/api/recipes/{recipe.slug}", headers=unique_user.token).json()
+    recipe_id = recipe_response["id"]
+    file_name = recipe_response["assets"][0]["fileName"]
+
+    media_response = api_client.get(f"/api/media/recipes/{recipe_id}/assets/{file_name}")
+    assert media_response.status_code == 200
+    assert "attachment" in media_response.headers["content-disposition"].lower()
+    assert media_response.headers["x-content-type-options"] == "nosniff"
+
+
 def test_recipe_image_upload(api_client: TestClient, unique_user: TestUser, recipe_ingredient_only: Recipe):
     data_payload = {"extension": "jpg"}
     file_payload = {"image": data.images_test_image_1.read_bytes()}
diff --git a/tests/unit_tests/test_config.py b/tests/unit_tests/test_config.py
index 8d0814d05..271884316 100644
--- a/tests/unit_tests/test_config.py
+++ b/tests/unit_tests/test_config.py
@@ -27,6 +27,31 @@ def test_non_default_settings(monkeypatch):
     assert app_settings.DOCS_URL is None
 
 
+def test_allowed_iframe_hosts_defaults(monkeypatch):
+    monkeypatch.delenv("ALLOWED_IFRAME_HOSTS", raising=False)
+    get_app_settings.cache_clear()
+    app_settings = get_app_settings()
+
+    # Secure defaults are always present and never empty (empty would disable iframe embeds).
+    assert "youtube.com" in app_settings.allowed_iframe_hosts
+    assert "vimeo.com" in app_settings.allowed_iframe_hosts
+
+
+def test_allowed_iframe_hosts_extends_defaults(monkeypatch):
+    monkeypatch.setenv("ALLOWED_IFRAME_HOSTS", " Example.com , trusted.tld ,, ")
+    get_app_settings.cache_clear()
+    app_settings = get_app_settings()
+
+    hosts = app_settings.allowed_iframe_hosts
+    # Configured hosts are normalized, blanks dropped, and defaults retained.
+    assert "example.com" in hosts
+    assert "trusted.tld" in hosts
+    assert "youtube.com" in hosts
+    assert "" not in hosts
+    # No duplicates.
+    assert len(hosts) == len(set(hosts))
+
+
 def test_default_connection_args(monkeypatch):
     monkeypatch.setenv("DB_ENGINE", "sqlite")
     get_app_settings.cache_clear()