software-mansion · hejsztynx · Jul 5, 2026 · Jul 5, 2026 · Jul 5, 2026 · Jul 6, 2026
diff --git a/.playwright/tests/links.spec.ts b/.playwright/tests/links.spec.ts
@@ -479,7 +479,7 @@ test.describe('test-links copy-paste', () => {
 
     await setTestLinksEditorHtml(
       page,
-      '<html><p><a href="custom://link">custom://link</a></p></html>'
+      '<html><p><a href="/custom-link">/custom-link</a></p></html>'
     );
 
     await copyWholeContent(editor);
@@ -488,7 +488,7 @@ test.describe('test-links copy-paste', () => {
 
     await expect
       .poll(async () => getTestLinksSerializedHtml(page))
-      .toContain('<a href="custom://link">custom://link</a>');
+      .toContain('<a href="/custom-link">/custom-link</a>');
   });
 });
 

diff --git a/apps/example-web/src/App.tsx b/apps/example-web/src/App.tsx
@@ -123,16 +123,16 @@ function App() {
 
   const handleUserMentionSelected = (item: MentionItem) => {
     ref.current?.setMention('@', `@${item.name}`, {
-      id: item.id,
-      type: 'user',
+      'id': item.id,
+      'data-type': 'user',
     });
     closeUserMentionPopup();
   };
 
   const handleChannelMentionSelected = (item: MentionItem) => {
     ref.current?.setMention('#', `#${item.name}`, {
-      id: item.id,
-      type: 'channel',
+      'id': item.id,
+      'data-type': 'channel',
     });
     closeChannelMentionPopup();
   };

diff --git a/cpp/parser/GumboNormalizer.c b/cpp/parser/GumboNormalizer.c
@@ -428,9 +428,10 @@ static void emit_attributes(GumboElement *el, const char *tag_name,
     if (gumbo_get_attribute(&el->attributes, "checked") != NULL)
       buffer_append_str(out, " checked");
   } else if (strcmp(tag_name, "mention") == 0) {
-    emit_one_attr(out, el, "id");
-    emit_one_attr(out, el, "text");
-    emit_one_attr(out, el, "indicator");
+    for (unsigned int i = 0; i < el->attributes.length; i++) {
+      GumboAttribute *attr = (GumboAttribute *)el->attributes.data[i];
+      emit_one_attr(out, el, attr->name);
+    }
   }
 }
 

diff --git a/cpp/tests/GumboParserTest.cpp b/cpp/tests/GumboParserTest.cpp
@@ -307,13 +307,20 @@ TEST(GumboParserTest, EnrichedTagRemappings) {
   EXPECT_EQ(
       GumboParser::normalizeHtml(
           "<mention text='@John Doe' indicator='@' id='1'>@John Doe</mention>"),
-      "<mention id=\"1\" text=\"@John Doe\" indicator=\"@\">@John "
+      "<mention text=\"@John Doe\" indicator=\"@\" id=\"1\">@John "
       "Doe</mention>");
   EXPECT_EQ(
       GumboParser::normalizeHtml("<mention text=\"@John Doe\" indicator=\"@\" "
                                  "id=\"1\">@John Doe</mention>"),
-      "<mention id=\"1\" text=\"@John Doe\" indicator=\"@\">@John "
+      "<mention text=\"@John Doe\" indicator=\"@\" id=\"1\">@John "
       "Doe</mention>");
+  // Custom mention attributes are preserved
+  EXPECT_EQ(
+      GumboParser::normalizeHtml(
+          "<mention id=\"1\" text=\"@John Doe\" indicator=\"@\" type=\"user\" "
+          "data-custom=\"custom data\">@John Doe</mention>"),
+      "<mention id=\"1\" text=\"@John Doe\" indicator=\"@\" type=\"user\" "
+      "data-custom=\"custom data\">@John Doe</mention>");
 
   // Link
   EXPECT_EQ(GumboParser::normalizeHtml(

diff --git a/docs/INPUT_API_REFERENCE.md b/docs/INPUT_API_REFERENCE.md
@@ -1043,7 +1043,7 @@ interface MentionStyleProperties {
 
 ### mention
 
-If only a single config is given, the style applies to all mention types. You can also set a different config for each mentionIndicator that has been defined, then the prop should be a record with indicators as a keys and configs as their values.
+If only a single config is given, the style applies to all mention types. You can also set a different config for each mentionIndicator that has been defined, then the prop should be a record with indicators as keys and configs as their values. Additionally, you can define a style using the `'default'` key, which will act as a base that the rest of your defined styles will fallback on.
 
 - `color` defines the color of mention's text, takes [color](https://reactnative.dev/docs/colors) value and defaults to `blue`.
 - `backgroundColor` is the mention's background color, takes [color](https://reactnative.dev/docs/colors) value and defaults to `yellow`.

diff --git a/docs/WEB.md b/docs/WEB.md
@@ -49,4 +49,11 @@ See [Web Keyboard Shortcuts](./INPUT_API_REFERENCE.md#web-keyboard-shortcuts) fo
 
 ## HTML sanitization
 
-You are responsible for sanitizing HTML on both input and output. The library does not guarantee safe or clean HTML output. This applies to any HTML you persist, render elsewhere, or accept from untrusted sources (XSS, paste attacks, etc.).
+On web, HTML is sanitized automatically with [DOMPurify](https://github.com/cure53/DOMPurify) on both input and output. This reduces XSS risk, but you should still treat untrusted HTML with caution and apply your own server-side sanitization.
+
+- **`EnrichedText`** sanitizes its `children` before rendering.
+- **`EnrichedTextInput`** sanitizes every HTML entry point — `defaultValue`, the `setValue` ref method, and pasted HTML — as well as its output from `getHTML` and the `onChangeHtml` callback.
+
+### Custom mention attributes
+
+To attach custom data to a mention, use the `data-` prefix (e.g. `data-user-id`) to make sure they survive sanitization. Attributes passed to the `setMention` ref method are properly sanitized.
diff --git a/src/web/EnrichedTextInput.tsx b/src/web/EnrichedTextInput.tsx
@@ -78,6 +78,10 @@ import { returnKeyTypeToEnterKeyHint } from './returnKeyTypeToEnterKeyHint';
 import { ENRICHED_TEXT_INPUT_CLASSNAME } from './constants/classNames';
 import { AutolinkPlugin } from './pmPlugins/AutolinkPlugin';
 import { useStableRef } from './useStableRef';
+import {
+  checkMentionAttributes,
+  sanitizeMentionAttributes,
+} from './sanitization/htmlSanitizer';
 
 function runFocused(
   editor: Editor,
@@ -351,7 +355,15 @@ export const EnrichedTextInput = ({
         indicator: string,
         text: string,
         attributes?: Record<string, string>
-      ) => setMention(editor, indicator, text, attributes),
+      ) => {
+        checkMentionAttributes(attributes);
+        setMention(
+          editor,
+          indicator,
+          text,
+          sanitizeMentionAttributes(attributes)
+        );
+      },
       setImage: (src: string, width: number, height: number) =>
         runFocused(editor, (c) => c.setImage({ src, width, height })),
       measure: () => {},

diff --git a/src/web/__tests__/htmlNormalizer.test.ts b/src/web/__tests__/htmlNormalizer.test.ts
@@ -285,14 +285,19 @@ describe('htmlNormalizer', () => {
         '<ul data-type="checkbox"><li checked>x</li></ul>',
       ],
 
-      // Mentions (note: cpp reorders attrs to id, text, indicator)
+      // Mentions
       [
         "<mention text='@John Doe' indicator='@' id='1'>@John Doe</mention>",
-        '<mention id="1" text="@John Doe" indicator="@">@John Doe</mention>',
+        '<mention text="@John Doe" indicator="@" id="1">@John Doe</mention>',
       ],
       [
         '<mention text="@John Doe" indicator="@" id="1">@John Doe</mention>',
-        '<mention id="1" text="@John Doe" indicator="@">@John Doe</mention>',
+        '<mention text="@John Doe" indicator="@" id="1">@John Doe</mention>',
+      ],
+      // Custom mention attributes are preserved
+      [
+        '<mention id="1" text="@John Doe" indicator="@" type="user" data-custom="custom data">@John Doe</mention>',
+        '<mention id="1" text="@John Doe" indicator="@" type="user" data-custom="custom data">@John Doe</mention>',
       ],
 
       // Link

diff --git a/src/web/__tests__/sanitization.test.ts b/src/web/__tests__/sanitization.test.ts
@@ -0,0 +1,113 @@
+import {
+  sanitizeHtml,
+  sanitizeMentionAttributes,
+  checkMentionAttributes,
+} from '../sanitization/htmlSanitizer';
+
+describe('sanitizeMentionAttributes', () => {
+  it('returns an empty object when given no attributes', () => {
+    expect(sanitizeMentionAttributes()).toEqual({});
+    expect(sanitizeMentionAttributes({})).toEqual({});
+  });
+
+  it('keeps data-* and commonly-allowed attributes', () => {
+    expect(
+      sanitizeMentionAttributes({
+        'data-user-id': '42',
+        'data-team': 'core',
+        'id': 'm1',
+        'class': 'highlight',
+      })
+    ).toEqual({
+      'data-user-id': '42',
+      'data-team': 'core',
+      'id': 'm1',
+      'class': 'highlight',
+    });
+  });
+
+  it('strips event handlers and unsafe attributes', () => {
+    const result = sanitizeMentionAttributes({
+      'onclick': 'alert(1)',
+      'onmouseover': 'steal()',
+      // eslint-disable-next-line no-script-url
+      'href': 'javascript:alert(1)',
+      'data-user-id': '42',
+    });
+    expect(result).toEqual({ 'data-user-id': '42' });
+  });
+
+  it('does not return the reserved text/indicator attributes', () => {
+    const result = sanitizeMentionAttributes({
+      'text': 'Joe',
+      'indicator': '@',
+      'data-user-id': '42',
+    });
+    expect(result).toEqual({ 'data-user-id': '42' });
+  });
+});
+
+describe('checkMentionAttributes', () => {
+  let warnSpy: jest.SpyInstance;
+
+  beforeEach(() => {
+    warnSpy = jest.spyOn(console, 'warn').mockImplementation(() => {});
+  });
+
+  afterEach(() => {
+    warnSpy.mockRestore();
+  });
+
+  it('does not warn for data-*, text, indicator, or commonly-allowed attributes', () => {
+    checkMentionAttributes({
+      'data-user-id': '42',
+      'text': 'Joe',
+      'indicator': '@',
+      'id': 'm1',
+      'class': 'x',
+      'style': 'color: red',
+    });
+    expect(warnSpy).not.toHaveBeenCalled();
+  });
+
+  it('warns for custom attributes without a recognized prefix', () => {
+    checkMentionAttributes({ foo: 'bar' });
+    expect(warnSpy).toHaveBeenCalledTimes(1);
+    expect(warnSpy.mock.calls[0][0]).toContain('foo');
+  });
+
+  it('does nothing when given no attributes', () => {
+    checkMentionAttributes();
+    expect(warnSpy).not.toHaveBeenCalled();
+  });
+});
+
+describe('sanitizeHtmlMention', () => {
+  it('keeps <mention> tags with text/indicator/data-* attributes', () => {
+    const out = sanitizeHtml(
+      '<mention text="Joe" indicator="@" data-user-id="42">@Joe</mention>'
+    );
+    expect(out).toContain('text="Joe"');
+    expect(out).toContain('indicator="@"');
+    expect(out).toContain('data-user-id="42"');
+  });
+
+  it('strips <mention> event handlers', () => {
+    expect(
+      sanitizeHtml('<mention onclick="alert(1)">x</mention>')
+    ).not.toContain('onclick');
+  });
+});
+
+describe('sanitizeLinkAttributes', () => {
+  it('strips javascript: URLs from links', () => {
+    const out = sanitizeHtml('<a href="javascript:alert(1)">x</a>');
+    // eslint-disable-next-line no-script-url
+    expect(out).not.toContain('javascript:');
+  });
+
+  it('strips unknown protocol URLs from links', () => {
+    const out = sanitizeHtml('<a href="custom://link">x</a>');
+    expect(out).not.toContain('custom');
+  });
+});
diff --git a/src/web/normalization/htmlNormalizer.ts b/src/web/normalization/htmlNormalizer.ts
@@ -255,12 +255,13 @@ function emitAttributes(el: Element, name: string): string {
     }
     case 'li':
       return el.hasAttribute('checked') ? ' checked' : '';
-    case 'mention':
-      return (
-        emitOneAttr(el, 'id') +
-        emitOneAttr(el, 'text') +
-        emitOneAttr(el, 'indicator')
-      );
+    case 'mention': {
+      let out = '';
+      for (const attr of Array.from(el.attributes)) {
+        out += emitOneAttr(el, attr.name);
+      }
+      return out;
+    }
     default:
       return '';
   }

diff --git a/src/web/normalization/tiptapHtmlNormalizer.ts b/src/web/normalization/tiptapHtmlNormalizer.ts
@@ -1,3 +1,4 @@
+import { sanitizeHtml } from '../sanitization/htmlSanitizer';
 import {
   checkboxHtmlForTiptap,
   checkboxHtmlFromTiptap,
@@ -8,6 +9,7 @@ export function prepareHtmlForTiptap(
   html: string,
   useHtmlNormalizer: boolean | undefined
 ): string {
+  html = sanitizeHtml(html);
   if (useHtmlNormalizer) {
     html = normalizeHtml(html);
   }
@@ -17,6 +19,7 @@ export function prepareHtmlForTiptap(
 }
 
 export function normalizeHtmlFromTiptap(html: string): string {
+  html = sanitizeHtml(html);
   html = checkboxHtmlFromTiptap(html);
 
   // Strip <p> wrappers inside <li> elements.

diff --git a/src/web/sanitization/htmlSanitizer.ts b/src/web/sanitization/htmlSanitizer.ts
@@ -1,8 +1,62 @@
 import DOMPurify from 'dompurify';
 
+const MENTION_ATTRS = ['text', 'indicator'];
+
+// Attributes DOMPurify keeps by default and are commonly used, so we don't emit an unnecessary warning
+const COMMONLY_ALLOWED_ATTRS = ['id', 'class', 'style'];
+
 export function sanitizeHtml(html: string) {
   return DOMPurify.sanitize(html, {
     ADD_TAGS: ['mention', 'codeblock'],
-    ADD_ATTR: ['text', 'indicator'],
+    ADD_ATTR: MENTION_ATTRS,
+  });
+}
+
+export function sanitizeMentionAttributes(
+  attributes?: Record<string, string>
+): Record<string, string> {
+  if (!attributes) return {};
+
+  const el = document.createElement('mention');
+  for (const [name, value] of Object.entries(attributes)) {
+    try {
+      el.setAttribute(name, value);
+    } catch {
+      // Ignore invalid attribute names.
+    }
+  }
+
+  const cleaned = new DOMParser()
+    .parseFromString(sanitizeHtml(el.outerHTML), 'text/html')
+    .querySelector('mention');
+
+  const out: Record<string, string> = {};
+  if (!cleaned) return out;
+
+  for (const attr of Array.from(cleaned.attributes)) {
+    if (MENTION_ATTRS.includes(attr.name.toLowerCase())) continue;
+    out[attr.name] = attr.value;
+  }
+  return out;
+}
+
+// Runtime warning: custom attributes without a "data-" prefix may be
+// removed by sanitization. This is a heuristic (it does not run DOMPurify).
+export function checkMentionAttributes(attributes?: Record<string, string>) {
+  if (!attributes) return;
+
+  Object.keys(attributes).forEach((attrName) => {
+    const lower = attrName.toLowerCase();
+    if (
+      lower.startsWith('data-') ||
+      MENTION_ATTRS.includes(lower) ||
+      COMMONLY_ALLOWED_ATTRS.includes(lower)
+    ) {
+      return;
+    }
+    console.warn(
+      `[EnrichedMention] Attribute "${attrName}" on the <mention> tag may be removed during sanitization. ` +
+        `Consider using the "data-" prefix for custom data attributes.`
+    );
   });
 }