CVE-2026-47733 - Rocket.Chat: Missing URL protocol sanitization in ImageElement allows javascript: URLs in markdown images

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MEDIUM

Rocket.Chat: Missing URL protocol sanitization in ImageElement allows javascript: URLs in markdown images

Published Jun 24, 2026

4.4

MEDIUM

CVSS 3.1

EPSS 0.18%

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.

Affected products

Vendor RocketChat Product Rocket.Chat Default
n/a
- Version
  < 8.5.0
  Status
  affected
  Constraints
  -

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor

Product

Default status

Versions

RocketChat

Rocket.Chat

n/a

Version	Status	Constraints
< 8.5.0	affected	-

Remediation

No remediation recorded yet.

Weaknesses (1)

CWE-79

Cross-site Scripting (XSS)

References (2)

https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-39089
Advisory
https://github.com/RocketChat/Rocket.Chat/security/advisories/GHSA-vvrf-fq54-q4pr
exploitx_refsource_CONFIRM

Link	Providers	Tags
https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-39089		Advisory
https://github.com/RocketChat/Rocket.Chat/security/advisories/GHSA-vvrf-fq54-q4pr		exploitx_refsource_CONFIRM