[newsfeed] add allowBasicHtmlTags option for basic emphasis (MagicMirrorOrg#4176)

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>
> - Does the pull request solve a **related** issue?
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Render a strict allowlist of basic formatting tags (b, strong, i, em, u)
in news titles and descriptions, while neutralizing all other HTML.

Feeds such as The Atlantic encode emphasis as entities (&lt;em&gt;),
which html-to-text decoded to a literal <em> string that the template
then auto-escaped, so the raw tag was shown on screen. The new opt-in
allowBasicHtmlTags option (default false) sanitizes both fields by
escaping everything and restoring only the exact, attribute-free
allowlisted tags, so the result is safe to render and arbitrary
HTML/script injection is impossible.

Adds unit tests for the sanitizer and an e2e test covering rendering and
an injection attempt.

Before screenshot: <img width="980" height="2726" alt="before"
src="https://github.com/user-attachments/assets/d1c871e1-21c5-44f9-ae40-da65c2c56f68"
/>
After screenshot: <img width="980" height="2726" alt="after"
src="https://github.com/user-attachments/assets/22d9e86b-221c-408e-a29b-718b0e98f236"
/>
> 3. Please run `node --run lint:prettier` before submitting so that
>    style issues are fixed.
Done

**Note**: Sometimes the development moves very fast. It is highly
recommended that you update your branch of `develop` before creating a
pull request to send us your changes. This makes everyone's lives
easier (including yours) and helps us out on the development team.

Thanks again and have a nice day!

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: egeekial

defaultmodules/newsfeed/newsfeed.js

@@ -33,7 +33,8 @@ Module.register("newsfeed", {
 		prohibitedWords: [],
 		scrollLength: 500,
 		logFeedWarnings: false,
-		dangerouslyDisableAutoEscaping: false
+		dangerouslyDisableAutoEscaping: false,
+		allowedBasicHtmlTags: []
 	},
 
 	getUrlPrefix (item) {

defaultmodules/newsfeed/newsfeed.njk

@@ -45,13 +45,13 @@
               {% if config.showPublishDate %}{{ item.publishDate }}:{% endif %}
             </div>
           {% endif %}
-          <div class="newsfeed-title bright medium light{{ ' no-wrap' if not config.wrapTitle }}">{{ escapeTitle(item.title, item.url, config.dangerouslyDisableAutoEscaping, config.showTitleAsUrl) }}</div>
+          <div class="newsfeed-title bright medium light{{ ' no-wrap' if not config.wrapTitle }}">{{ escapeTitle(item.title, item.url, config.dangerouslyDisableAutoEscaping or (config.allowedBasicHtmlTags | length), config.showTitleAsUrl) }}</div>
           {% if config.showDescription %}
             <div class="newsfeed-desc small light{{ ' no-wrap' if not config.wrapDescription }}">
               {% if config.truncDescription %}
-                {{ escapeText(item.description | truncate(config.lengthDescription) , config.dangerouslyDisableAutoEscaping) }}
+                {{ escapeText(item.description | truncate(config.lengthDescription) , config.dangerouslyDisableAutoEscaping or (config.allowedBasicHtmlTags | length)) }}
               {% else %}
-                {{ escapeText(item.description, config.dangerouslyDisableAutoEscaping) }}
+                {{ escapeText(item.description, config.dangerouslyDisableAutoEscaping or (config.allowedBasicHtmlTags | length)) }}
               {% endif %}
             </div>
           {% endif %}
@@ -68,13 +68,13 @@
           {% if config.showPublishDate %}{{ publishDate }}:{% endif %}
         </div>
       {% endif %}
-      <div class="newsfeed-title bright medium light{{ ' no-wrap' if not config.wrapTitle }}">{{ escapeTitle(title, url, config.dangerouslyDisableAutoEscaping, config.showTitleAsUrl) }}</div>
+      <div class="newsfeed-title bright medium light{{ ' no-wrap' if not config.wrapTitle }}">{{ escapeTitle(title, url, config.dangerouslyDisableAutoEscaping or (config.allowedBasicHtmlTags | length), config.showTitleAsUrl) }}</div>
       {% if config.showDescription %}
         <div class="newsfeed-desc small light{{ ' no-wrap' if not config.wrapDescription }}">
           {% if config.truncDescription %}
-            {{ escapeText(description | truncate(config.lengthDescription) , config.dangerouslyDisableAutoEscaping) }}
+            {{ escapeText(description | truncate(config.lengthDescription) , config.dangerouslyDisableAutoEscaping or (config.allowedBasicHtmlTags | length)) }}
           {% else %}
-            {{ escapeText(description, config.dangerouslyDisableAutoEscaping) }}
+            {{ escapeText(description, config.dangerouslyDisableAutoEscaping or (config.allowedBasicHtmlTags | length)) }}
           {% endif %}
         </div>
       {% endif %}

defaultmodules/newsfeed/newsfeedfetcher.js

@@ -6,6 +6,26 @@ const { htmlToText } = require("html-to-text");
 const Log = require("logger");
 const HTTPFetcher = require("#http_fetcher");
 
+// The complete set of basic formatting tags users are allowed to opt into via the
+// `allowedBasicHtmlTags` config option. These are inline emphasis / line-break tags that
+// never carry attributes once sanitized, so they cannot be used for injection. Anything
+// requested outside this list is ignored (see the constructor).
+const SAFE_HTML_TAGS = ["b", "strong", "i", "em", "u", "br", "code", "s", "sub", "sup"];
+
+// html-to-text formatter that re-emits an allowed inline tag around its content,
+// so feeds that send real <em>/<strong> elements keep their emphasis. `br` is a void
+// element, so it is emitted as a single self-contained tag with no children/closing tag.
+const keepTagFormatter = (elem, walk, builder, formatOptions) => {
+	const { tagName } = formatOptions;
+	if (tagName === "br") {
+		builder.addLiteral("<br>");
+		return;
+	}
+	builder.addLiteral(`<${tagName}>`);
+	walk(elem.children, builder);
+	builder.addLiteral(`</${tagName}>`);
+};
+
 /**
  * NewsfeedFetcher - Fetches and parses RSS/Atom feed data
  * Uses HTTPFetcher for HTTP handling with intelligent error handling
@@ -20,12 +40,22 @@ class NewsfeedFetcher {
 	 * @param {string} encoding - Encoding of the feed (e.g., 'UTF-8')
 	 * @param {boolean} logFeedWarnings - If true log warnings when there is an error parsing a news article
 	 * @param {boolean} useCorsProxy - If true cors proxy is used for article url's
+	 * @param {string[]} allowedBasicHtmlTags - Basic formatting tags to keep in title and description. Only tags from the safe list are honored; anything else is ignored.
 	 */
-	constructor (url, reloadInterval, encoding, logFeedWarnings, useCorsProxy) {
+	constructor (url, reloadInterval, encoding, logFeedWarnings, useCorsProxy, allowedBasicHtmlTags = []) {
 		this.url = url;
 		this.encoding = encoding;
 		this.logFeedWarnings = logFeedWarnings;
 		this.useCorsProxy = useCorsProxy;
+
+		// Keep only tags from the hardcoded safe list; warn about (and ignore) anything else.
+		const requestedTags = (Array.isArray(allowedBasicHtmlTags) ? allowedBasicHtmlTags : []).map((tag) => String(tag).trim().toLowerCase());
+		this.allowedBasicHtmlTags = requestedTags.filter((tag) => SAFE_HTML_TAGS.includes(tag));
+		const ignoredTags = requestedTags.filter((tag) => !SAFE_HTML_TAGS.includes(tag));
+		if (ignoredTags.length > 0) {
+			Log.warn(`Ignoring unsupported allowedBasicHtmlTags [${ignoredTags.join(", ")}] for url ${url}. Allowed tags are: ${SAFE_HTML_TAGS.join(", ")}`);
+		}
+
 		this.items = [];
 		this.fetchFailedCallback = () => {};
 		this.itemsReceivedCallback = () => {};
@@ -44,6 +74,48 @@ class NewsfeedFetcher {
 		this.httpFetcher.on("error", (errorInfo) => this.fetchFailedCallback(this, errorInfo));
 	}
 
+	/**
+	 * Sanitizes a feed string, keeping only the given allowlist of basic
+	 * formatting tags and neutralizing everything else.
+	 *
+	 * The approach is allowlist-only and therefore safe to render unescaped:
+	 * html-to-text first strips all real markup (scripts, links, images, …) and
+	 * decodes entities to text, then EVERYTHING is HTML-escaped and ONLY the exact,
+	 * attribute-free allowlisted tags are restored. No attributes, event handlers,
+	 * or other tags can survive, so arbitrary HTML/script injection is impossible.
+	 * @param {string} html - The raw title or description from the feed.
+	 * @param {string[]} [allowedTags] - Tags to keep. Callers pass an already-validated subset of SAFE_HTML_TAGS.
+	 * @returns {string} Safe HTML containing at most the allowed formatting tags.
+	 */
+	static sanitizeBasicHtml (html, allowedTags = []) {
+		// `br` keeps its default "collapse to a space" behavior unless explicitly allowed.
+		const keepTagSelectors = allowedTags.map((tagName) => ({ selector: tagName, format: "keepTag", options: { tagName } }));
+
+		const text = htmlToText(html, {
+			wordwrap: false,
+			formatters: { keepTag: keepTagFormatter },
+			selectors: [
+				{ selector: "a", options: { ignoreHref: true, noAnchorUrl: true } },
+				{ selector: "br", format: "inlineSurround", options: { prefix: " " } },
+				{ selector: "img", format: "skip" },
+				...keepTagSelectors
+			]
+		});
+
+		const escaped = text
+			.replaceAll("&", "&amp;")
+			.replaceAll("<", "&lt;")
+			.replaceAll(">", "&gt;");
+
+		if (allowedTags.length === 0) {
+			return escaped;
+		}
+
+		// Restore only the exact, attribute-free allowed opening/closing tags after escaping.
+		const restoreAllowedTags = new RegExp(`&lt;(/?(?:${allowedTags.join("|")}))&gt;`, "g");
+		return escaped.replace(restoreAllowedTags, "<$1>");
+	}
+
 	/**
 	 * Creates a parse error info object
 	 * @param {string} message - Error message
@@ -84,22 +156,30 @@ class NewsfeedFetcher {
 			const url = item.url || item.link || "";
 
 			if (title && pubdate) {
-				// Convert HTML entities, codes and tag
-				description = htmlToText(description, {
-					wordwrap: false,
-					selectors: [
-						{ selector: "a", options: { ignoreHref: true, noAnchorUrl: true } },
-						{ selector: "br", format: "inlineSurround", options: { prefix: " " } },
-						{ selector: "img", format: "skip" }
-					]
-				});
+				let displayTitle = title;
+				if (this.allowedBasicHtmlTags.length > 0) {
+					// Keep the configured basic formatting tags in both fields, strip everything else
+					description = NewsfeedFetcher.sanitizeBasicHtml(description, this.allowedBasicHtmlTags);
+					displayTitle = NewsfeedFetcher.sanitizeBasicHtml(title, this.allowedBasicHtmlTags);
+				} else {
+					// Convert HTML entities, codes and tag
+					description = htmlToText(description, {
+						wordwrap: false,
+						selectors: [
+							{ selector: "a", options: { ignoreHref: true, noAnchorUrl: true } },
+							{ selector: "br", format: "inlineSurround", options: { prefix: " " } },
+							{ selector: "img", format: "skip" }
+						]
+					});
+				}
 
 				this.items.push({
-					title,
+					title: displayTitle,
 					description,
 					pubdate,
 					url,
 					useCorsProxy: this.useCorsProxy,
+					// Hash on the original title so the dedup identity is stable regardless of allowedBasicHtmlTags
 					hash: crypto.createHash("sha256").update(`${pubdate} :: ${title} :: ${url}`).digest("hex")
 				});
 			} else if (this.logFeedWarnings) {

defaultmodules/newsfeed/node_helper.js

@@ -61,7 +61,7 @@ module.exports = NodeHelper.create({
 		let fetcher;
 		if (typeof this.fetchers[url] === "undefined") {
 			Log.log(`Create new newsfetcher for url: ${url} - Interval: ${reloadInterval}`);
-			fetcher = new NewsfeedFetcher(url, reloadInterval, encoding, config.logFeedWarnings, useCorsProxy);
+			fetcher = new NewsfeedFetcher(url, reloadInterval, encoding, config.logFeedWarnings, useCorsProxy, config.allowedBasicHtmlTags);
 
 			fetcher.onReceive(() => {
 				this.broadcastFeeds();

tests/configs/modules/newsfeed/basic_html.js

@@ -0,0 +1,28 @@
+let config = {
+	address: "0.0.0.0",
+	ipWhitelist: [],
+	timeFormat: 12,
+
+	modules: [
+		{
+			module: "newsfeed",
+			position: "bottom_bar",
+			config: {
+				feeds: [
+					{
+						title: "Formatting Feed",
+						url: "http://localhost:8080/tests/mocks/newsfeed_basic_html.xml"
+					}
+				],
+				showDescription: true,
+				truncDescription: false,
+				allowedBasicHtmlTags: ["b", "strong", "i", "em", "u", "br", "code", "s", "sub", "sup"]
+			}
+		}
+	]
+};
+
+/*************** DO NOT EDIT THE LINE BELOW ***************/
+if (typeof module !== "undefined") {
+	module.exports = config;
+}

tests/e2e/modules/newsfeed_spec.js

@@ -45,6 +45,32 @@ const runTests = () => {
 		});
 	});
 
+	describe("Basic HTML tags", () => {
+		beforeAll(async () => {
+			await helpers.startApplication("tests/configs/modules/newsfeed/basic_html.js");
+			await helpers.getDocument();
+			page = helpers.getPage();
+		});
+
+		it("should render allowlisted formatting tags in title and description", async () => {
+			await expect(page.locator(".newsfeed .newsfeed-desc")).toBeVisible();
+			const descHtml = await page.locator(".newsfeed .newsfeed-desc").innerHTML();
+			expect(descHtml).toContain("<em>");
+			expect(descHtml).toContain("<strong>");
+			expect(descHtml).toContain("<u>");
+			const titleHtml = await page.locator(".newsfeed .newsfeed-title").innerHTML();
+			expect(titleHtml).toContain("<em>");
+		});
+
+		it("should strip disallowed HTML and not execute injected scripts", async () => {
+			const descHtml = await page.locator(".newsfeed .newsfeed-desc").innerHTML();
+			expect(descHtml).not.toContain("<script");
+			expect(descHtml).not.toContain("onerror");
+			const xss = await page.evaluate(() => window.__newsfeedXss);
+			expect(xss).toBeUndefined();
+		});
+	});
+
 	describe("Invalid configuration", () => {
 		beforeAll(async () => {
 			await helpers.startApplication("tests/configs/modules/newsfeed/incorrect_url.js");

tests/mocks/newsfeed_basic_html.xml

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<rss version="2.0">
+  <channel>
+    <title>Formatting Feed</title>
+    <link>http://localhost:8080</link>
+    <description>Feed used to test the allowBasicHtmlTags option.</description>
+    <item>
+      <title>News &lt;em&gt;Flash&lt;/em&gt;</title>
+      <link>http://localhost:8080/article</link>
+      <pubDate>Tue, 20 Sep 2016 11:16:08 +0000</pubDate>
+      <guid isPermaLink="false">http://localhost:8080/?p=1</guid>
+      <description><![CDATA[<p><em>Italic</em> and <strong>Bold</strong> and <u>Underlined</u> text.</p><script>window.__newsfeedXss = true;</script><img src="x" onerror="window.__newsfeedXss = true">]]></description>
+    </item>
+  </channel>
+</rss>

tests/unit/modules/default/newsfeed/newsfeedfetcher_spec.js

@@ -0,0 +1,83 @@
+const defaults = require("../../../../../js/defaults");
+
+const NewsfeedFetcher = require(`../../../../../${defaults.defaultModulesDir}/newsfeed/newsfeedfetcher`);
+
+// The full safe list users may opt into; most tests run with it enabled.
+const ALL_TAGS = ["b", "strong", "i", "em", "u", "br", "code", "s", "sub", "sup"];
+const sanitize = (html, allowedTags = ALL_TAGS) => NewsfeedFetcher.sanitizeBasicHtml(html, allowedTags);
+
+describe("NewsfeedFetcher.sanitizeBasicHtml", () => {
+	it("keeps real basic formatting tags", () => {
+		expect(sanitize("<b>a</b> <strong>b</strong> <i>c</i> <em>d</em> <u>e</u>"))
+			.toBe("<b>a</b> <strong>b</strong> <i>c</i> <em>d</em> <u>e</u>");
+	});
+
+	it("keeps the additional safe tags (code, s, sub, sup)", () => {
+		expect(sanitize("<code>x</code> <s>y</s> <sub>z</sub> <sup>w</sup>"))
+			.toBe("<code>x</code> <s>y</s> <sub>z</sub> <sup>w</sup>");
+	});
+
+	it("renders entity-encoded formatting tags (e.g. The Atlantic feed)", () => {
+		// Feeds like theatlantic.com ship emphasis as escaped entities
+		expect(sanitize("the &lt;em&gt;Atlantic&lt;/em&gt; ocean")).toBe("the <em>Atlantic</em> ocean");
+	});
+
+	it("handles emphasis inside titles regardless of how the parser delivers it", () => {
+		// The Atlantic uses <em> in titles, e.g. "That's Enough, <em>Euphoria</em>"
+		const expected = "That’s Enough, <em>Euphoria</em>";
+		expect(sanitize("That’s Enough, <em>Euphoria</em>")).toBe(expected);
+		expect(sanitize("That’s Enough, &lt;em&gt;Euphoria&lt;/em&gt;")).toBe(expected);
+	});
+
+	it("strips attributes from allowed tags", () => {
+		const result = sanitize("<b onclick=\"steal()\" class=\"x\">bold</b>");
+		expect(result).toBe("<b>bold</b>");
+		expect(result).not.toContain("onclick");
+		expect(result).not.toContain("class");
+	});
+
+	it("neutralizes script tags", () => {
+		expect(sanitize("<script>alert(1)</script>hello")).not.toContain("<script");
+		// Entity-encoded scripts must stay inert text, never become live markup
+		const encoded = sanitize("&lt;script&gt;alert(1)&lt;/script&gt;");
+		expect(encoded).not.toContain("<script");
+		expect(encoded).toContain("&lt;script&gt;");
+	});
+
+	it("drops images and link hrefs but keeps disallowed-tag text", () => {
+		const result = sanitize("<img src=\"x\" onerror=\"alert(1)\"><a href=\"https://evil.example\">link</a><h1>title</h1>");
+		expect(result).not.toContain("onerror");
+		expect(result).not.toContain("href");
+		expect(result).not.toContain("<h1>");
+		expect(result).toContain("link");
+		expect(result.toLowerCase()).toContain("title");
+	});
+
+	it("escapes bare HTML special characters in plain text", () => {
+		expect(sanitize("Fish &amp; Chips for &lt; 5")).toBe("Fish &amp; Chips for &lt; 5");
+	});
+
+	it("only keeps tags present in the supplied allowlist", () => {
+		// Allow just <em>: a safe-but-not-allowed <strong> must become plain text.
+		const result = sanitize("<em>kept</em> <strong>dropped</strong>", ["em"]);
+		expect(result).toBe("<em>kept</em> dropped");
+		expect(result).not.toContain("<strong>");
+	});
+
+	it("escapes everything when the allowlist is empty", () => {
+		expect(sanitize("<em>hi</em> &amp; <b>bye</b>", [])).toBe("hi &amp; bye");
+	});
+
+	it("renders <br> as a single self-closing tag when allowed", () => {
+		const result = sanitize("a<br>b", ["br"]);
+		expect(result).toContain("<br>");
+		expect(result).not.toContain("<br></br>");
+		expect(result).not.toContain("&lt;br&gt;");
+	});
+
+	it("collapses <br> to a space when not allowed", () => {
+		const result = sanitize("a<br>b", ["em"]);
+		expect(result).not.toContain("<br>");
+		expect(result).toBe("a b");
+	});
+});