CVE-2026-47733 Rocket.Chat: Missing URL protocol sanitization in ImageElement allows javascript: URLs in markdown images
Authenticated users can inject JavaScript via markdown images, potentially executing code in viewers' sessions.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-47733?
CVE-2026-47733 is a medium-severity cross-site scripting vulnerability in RocketChat Rocket.Chat, published on 24 Jun 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-79
Which versions are affected by CVE-2026-47733?
How do I fix CVE-2026-47733?
No fix has been published for CVE-2026-47733 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-47733 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-47733 exists.
Sources
Also known as GHSA-vvrf-fq54-q4pr.