fix(previews): no genuine preview card for a site a deceptive link only pretends to be (#286)

Previews are built from the plain body, clicks follow formatted_body's
hrefs, and a sender controls both: text "https://paypal.com" linked to
evil.example showed a real PayPal card. Drop body URLs whose site is
only claimed by the visible text of a mismatched link (linkSafety).

Fixes #286

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

src/app/components/AccountDataEditor.tsx

@@ -297,7 +297,7 @@ export function AccountDataEditor({
             </Chip>
           </Box>
           <Box shrink="No">
-            <IconButton onClick={requestClose} variant="Surface" aria-label="Close">
+            <IconButton type="button" onClick={requestClose} variant="Surface" aria-label="Close">
               <Icon src={Icons.Cross} />
             </IconButton>
           </Box>

src/app/components/DeviceVerificationSetup.tsx

@@ -315,7 +315,7 @@ export const DeviceVerificationSetup = forwardRef<HTMLDivElement, DeviceVerifica
               Setup Device Verification
             </Text>
           </Box>
-          <IconButton size="300" radii="300" onClick={onCancel} aria-label="Cancel">
+          <IconButton type="button" size="300" radii="300" onClick={onCancel} aria-label="Cancel">
             <Icon src={Icons.Cross} />
           </IconButton>
         </Header>
@@ -361,7 +361,7 @@ export const DeviceVerificationReset = forwardRef<HTMLDivElement, DeviceVerifica
               Reset Device Verification
             </Text>
           </Box>
-          <IconButton size="300" radii="300" onClick={onCancel} aria-label="Cancel">
+          <IconButton type="button" size="300" radii="300" onClick={onCancel} aria-label="Cancel">
             <Icon src={Icons.Cross} />
           </IconButton>
         </Header>

src/app/components/create-room/utils.ts

@@ -139,8 +139,11 @@ export const createRoom = async (mx: MatrixClient, data: CreateRoomData): Promis
       data.allowFederation,
       data.additionalCreators,
     ),
-    power_level_content_override:
-      data.type === RoomType.Call ? createVoiceRoomPowerLevelsOverride() : undefined,
+    // [Gitea #328] Every non-space room gets call.member at user level, not just
+    // voice rooms: the call button is shown in private group rooms too, and with
+    // Synapse's state_default (50) only admins could start or join a call there
+    // ("You don't have permission to join!").
+    power_level_content_override: createVoiceRoomPowerLevelsOverride(),
     initial_state: initialState,
   };
 

src/app/components/message/MsgTypeRenderers.tsx

@@ -40,6 +40,7 @@ import { parseGeoUri, scaleYDimension } from '../../utils/common';
 import { formatAccuracy } from '../../utils/geoShare';
 import { Attachment, AttachmentBox, AttachmentContent, AttachmentHeader } from './attachment';
 import { FileHeader, FileDownloadButton } from './FileHeader';
+import { previewUrlsFor } from '../../utils/linkSafety';
 
 // ≈ 20 lines; in rem so a larger font setting doesn't show fewer lines (Gitea #343).
 const COLLAPSE_MAX_HEIGHT_REM = 20;
@@ -343,7 +344,13 @@ export function MText({
   if (typeof body !== 'string') return <BrokenContent />;
   const trimmedBody = trimReplyFromBody(body);
   const urlsMatch = renderUrlsPreview && trimmedBody.match(URL_REG);
-  const urls = urlsMatch ? [...new Set(urlsMatch)] : undefined;
+  // [Gitea #286] no genuine card for a site a deceptive link only pretends to be
+  const urls = urlsMatch
+    ? previewUrlsFor(
+        [...new Set(urlsMatch)],
+        typeof customBody === 'string' ? customBody : undefined,
+      )
+    : undefined;
 
   return (
     <>
@@ -401,7 +408,13 @@ export function MEmote({
   if (typeof body !== 'string') return <BrokenContent />;
   const trimmedBody = trimReplyFromBody(body);
   const urlsMatch = renderUrlsPreview && trimmedBody.match(URL_REG);
-  const urls = urlsMatch ? [...new Set(urlsMatch)] : undefined;
+  // [Gitea #286] no genuine card for a site a deceptive link only pretends to be
+  const urls = urlsMatch
+    ? previewUrlsFor(
+        [...new Set(urlsMatch)],
+        typeof customBody === 'string' ? customBody : undefined,
+      )
+    : undefined;
 
   return (
     <>
@@ -458,7 +471,13 @@ export function MNotice({
   if (typeof body !== 'string') return <BrokenContent />;
   const trimmedBody = trimReplyFromBody(body);
   const urlsMatch = renderUrlsPreview && trimmedBody.match(URL_REG);
-  const urls = urlsMatch ? [...new Set(urlsMatch)] : undefined;
+  // [Gitea #286] no genuine card for a site a deceptive link only pretends to be
+  const urls = urlsMatch
+    ? previewUrlsFor(
+        [...new Set(urlsMatch)],
+        typeof customBody === 'string' ? customBody : undefined,
+      )
+    : undefined;
 
   return (
     <>

src/app/features/common-settings/developer-tools/StateEventEditor.tsx

@@ -275,7 +275,7 @@ export function StateEventEditor({ type, stateKey, requestClose }: StateEventEdi
             </Chip>
           </Box>
           <Box shrink="No">
-            <IconButton onClick={requestClose} variant="Surface" aria-label="Close">
+            <IconButton type="button" onClick={requestClose} variant="Surface" aria-label="Close">
               <Icon src={Icons.Cross} />
             </IconButton>
           </Box>

src/app/features/room/PollCreator.tsx

@@ -143,7 +143,7 @@ export function PollCreator({ roomId, threadRootId, onClose }: PollCreatorProps)
                   Create Poll
                 </Text>
               </Box>
-              <IconButton size="300" radii="300" onClick={onClose} aria-label="Close">
+              <IconButton type="button" size="300" radii="300" onClick={onClose} aria-label="Close">
                 <Icon src={Icons.Cross} />
               </IconButton>
             </Header>

src/app/features/room/ReportRoomModal.tsx

@@ -118,7 +118,7 @@ export function ReportRoomModal({ roomId, onClose }: ReportRoomModalProps) {
                   Report Room
                 </Text>
               </Box>
-              <IconButton size="300" onClick={onClose} radii="300" aria-label="Close">
+              <IconButton type="button" size="300" onClick={onClose} radii="300" aria-label="Close">
                 <Icon src={Icons.Cross} />
               </IconButton>
             </Header>

src/app/features/room/ReportUserModal.tsx

@@ -124,7 +124,7 @@ export function ReportUserModal({ userId, onClose }: ReportUserModalProps) {
                   Report User
                 </Text>
               </Box>
-              <IconButton size="300" onClick={onClose} radii="300" aria-label="Close">
+              <IconButton type="button" size="300" onClick={onClose} radii="300" aria-label="Close">
                 <Icon src={Icons.Cross} />
               </IconButton>
             </Header>

src/app/features/room/ScheduleMessageModal.tsx

@@ -202,7 +202,7 @@ export function ScheduleMessageModal({
                   {title}
                 </Text>
               </Box>
-              <IconButton size="300" radii="300" onClick={onClose} aria-label="Close">
+              <IconButton type="button" size="300" radii="300" onClick={onClose} aria-label="Close">
                 <Icon src={Icons.Cross} />
               </IconButton>
             </Header>

src/app/features/room/message/Message.tsx

@@ -725,7 +725,13 @@ export const MessageDeleteItem = as<
                     Delete Message
                   </Text>
                 </Box>
-                <IconButton size="300" onClick={handleClose} radii="300" aria-label="Close">
+                <IconButton
+                  type="button"
+                  size="300"
+                  onClick={handleClose}
+                  radii="300"
+                  aria-label="Close"
+                >
                   <Icon src={Icons.Cross} />
                 </IconButton>
               </Header>
@@ -865,7 +871,13 @@ export const MessageReportItem = as<
                     Report Message
                   </Text>
                 </Box>
-                <IconButton size="300" onClick={handleClose} radii="300" aria-label="Close">
+                <IconButton
+                  type="button"
+                  size="300"
+                  onClick={handleClose}
+                  radii="300"
+                  aria-label="Close"
+                >
                   <Icon src={Icons.Cross} />
                 </IconButton>
               </Header>

src/app/features/room/message/Reactions.tsx

@@ -69,8 +69,15 @@ export const Reactions = as<'div', ReactionsProps>(
     const measure = useCallback(() => {
       const container = containerRef.current;
       if (!container) return;
-      const rowWidth = container.getBoundingClientRect().width;
-      const gap = parseFloat(getComputedStyle(container).columnGap) || 8;
+      // [Gitea #305] The width the chips actually get (content box). The border
+      // box grows by 4 px while collapsed (margin -2 / padding 2), and measuring
+      // it made a row within 4 px of fitting flip collapsed↔expanded every frame.
+      const cs = getComputedStyle(container);
+      const rowWidth =
+        container.clientWidth -
+        (parseFloat(cs.paddingLeft) || 0) -
+        (parseFloat(cs.paddingRight) || 0);
+      const gap = parseFloat(cs.columnGap) || 8;
       const chips = keys ? keys.split('\u0000').map((k) => chipRefs.current.get(k)) : [];
       const widths = chips.map((el) => el?.getBoundingClientRect().width ?? 0);
       const moreWidth = moreRef.current?.getBoundingClientRect().width ?? 48;
@@ -110,8 +117,21 @@ export const Reactions = as<'div', ReactionsProps>(
         style={{
           ...props.style,
           ...(collapsed && rowHeight
-            ? // 2px breathing room so row-1 focus outlines are not clipped.
-              { maxHeight: rowHeight + 4, overflow: 'hidden', padding: 2, margin: -2 }
+            ? // 2px breathing room so row-1 focus outlines are not clipped. Longhand
+              // margins so the timeline's marginTop survives (Gitea #305: the
+              // `margin` shorthand overrode it and, once removed, cleared it).
+              {
+                maxHeight: rowHeight + 4,
+                overflow: 'hidden',
+                padding: 2,
+                marginLeft: -2,
+                marginRight: -2,
+                marginBottom: -2,
+                marginTop:
+                  props.style?.marginTop !== undefined
+                    ? `calc(${typeof props.style.marginTop === 'number' ? `${props.style.marginTop}px` : props.style.marginTop} - 2px)`
+                    : -2,
+              }
             : {}),
         }}
         ref={(el) => {

src/app/utils/linkSafety.test.ts

@@ -1,6 +1,6 @@
 import { test } from 'node:test';
 import assert from 'node:assert/strict';
-import { analyzeLink, hostFromText, registrableDomain } from './linkSafety';
+import { analyzeLink, hostFromText, previewUrlsFor, registrableDomain } from './linkSafety';
 
 test('visible text that names another site is a mismatch', () => {
   const r = analyzeLink('https://matrix.lotusguild.org/login', 'https://evil.example/login');
@@ -73,3 +73,25 @@ test('shared hosting suffixes are separate sites (#335)', () => {
   );
   assert.equal(registrableDomain('news.bbc.co.uk'), 'bbc.co.uk');
 });
+
+test('previewUrlsFor: no preview for a site a deceptive link only claims (#286)', () => {
+  const urls = ['https://paypal.com'];
+  assert.deepEqual(
+    previewUrlsFor(urls, '<a href="https://evil.example/login">https://paypal.com</a>'),
+    [],
+  );
+  // An honest link keeps its preview.
+  assert.deepEqual(
+    previewUrlsFor(urls, '<a href="https://www.paypal.com/x">https://paypal.com</a>'),
+    urls,
+  );
+  assert.deepEqual(previewUrlsFor(urls, undefined), urls);
+  // Other links in the message keep theirs.
+  assert.deepEqual(
+    previewUrlsFor(
+      ['https://paypal.com', 'https://lotusguild.org'],
+      'see <a href="https://evil.example">paypal.com</a> and https://lotusguild.org',
+    ),
+    ['https://lotusguild.org'],
+  );
+});

src/app/utils/linkSafety.ts

@@ -221,3 +221,37 @@ export const analyzeLink = (text: string, href: string): LinkSafety | null => {
   const other = shown.find((h) => registrableDomain(h) !== realSite);
   return { mismatch: other !== undefined, shownHost: other ?? shown[0], realHost, punycode };
 };
+
+const ANCHOR_REG = /<a\s[^>]*href\s*=\s*(["'])(.*?)\1[^>]*>([\s\S]*?)<\/a>/gi;
+const decodeEntities = (s: string): string =>
+  s
+    .replace(/<[^>]+>/g, '')
+    .replace(/&quot;/g, '"')
+    .replace(/&#39;/g, "'")
+    .replace(/&lt;/g, '<')
+    .replace(/&gt;/g, '>')
+    .replace(/&amp;/g, '&');
+
+/**
+ * [Gitea #286] The URLs to build link previews for. Previews come from the
+ * plain `body`, but clicks follow `formatted_body`'s hrefs, and a sender
+ * controls both: text reading "https://paypal.com" linked to evil.example got
+ * a genuine PayPal card. Drop any body URL whose site is only *claimed* by a
+ * deceptive link's text.
+ */
+export const previewUrlsFor = (urls: string[], formattedBody: string | undefined): string[] => {
+  if (!formattedBody || urls.length === 0) return urls;
+  const claimed = new Set<string>();
+  Array.from(formattedBody.matchAll(ANCHOR_REG)).forEach((m) => {
+    const safety = analyzeLink(decodeEntities(m[3]), decodeEntities(m[2]));
+    if (safety?.mismatch && safety.shownHost) claimed.add(registrableDomain(safety.shownHost));
+  });
+  if (claimed.size === 0) return urls;
+  return urls.filter((u) => {
+    try {
+      return !claimed.has(registrableDomain(new URL(u).hostname));
+    } catch {
+      return true;
+    }
+  });
+};