CVE-2026-47733
Rocket.Chat: Missing URL protocol sanitization in ImageElement allows javascript: URLs in markdown images
Description
Rocket.Chat is an open-source, secure, fully customizable communications platform. Prior to 8.5.0, the ImageElement component in packages/gazzodown renders user-controlled src values directly into <a href> and <img src> attributes without protocol sanitization. Unlike the analogous LinkSpan component — which uses sanitizeUrl to block javascript:, data:, and vbscript: protocols — ImageElement passes the raw URL through unchanged. An authenticated user can post a markdown image with a javascript: URL that, if clicked on an older browser, would execute arbitrary JavaScript in the viewer's session. This vulnerability is fixed in 8.5.0.
INFO
Published Date :
June 24, 2026, 8:51 p.m.
Last Modified :
June 24, 2026, 8:51 p.m.
Remotely Exploit :
Yes !
Source :
GitHub_M
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update Rocket.Chat to version 8.5.0 or later.
- Review markdown image URLs for malicious content.
- Sanitize user-supplied URL input on the server.
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