CVE-2026-47733

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.

Score

CVSS 3.1 4.4 Medium

Status

Deferred - security-advisories@github.com

Published

2026-06-24

Last modified

2026-10-25

Weaknesses

CWE-79

Affected products

• Rocket.chat (Rocketchat)

References

• https://github.com/RocketChat/Rocket.Chat/security/advisories/GHSA-vvrf-fq54-q4pr