CVE-2026-47733: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in RocketChat Rocket.Chat
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.
AI Analysis
Technical Summary
Rocket.Chat before version 8.5.0 contains a CWE-79 improper input neutralization vulnerability in the ImageElement component within packages/gazzodown. Unlike the LinkSpan component, which sanitizes URLs to block dangerous protocols such as javascript:, data:, and vbscript:, ImageElement does not sanitize the protocol of user-supplied src attributes. This allows an authenticated user to craft markdown images with javascript: URLs that, if clicked on older browsers, can execute arbitrary JavaScript in the context of the viewer's session. This vulnerability has a CVSS 3.1 base score of 4.4, indicating medium severity, and is fixed in Rocket.Chat 8.5.0.
Potential Impact
An authenticated user can exploit this vulnerability to execute arbitrary JavaScript in the context of another user's session by posting a specially crafted markdown image with a javascript: URL. This could lead to limited confidentiality and integrity impacts, such as session hijacking or user interface manipulation, but does not affect availability. The attack requires user interaction (clicking the malicious link) and has a high attack complexity.
Mitigation Recommendations
This vulnerability is fixed in Rocket.Chat version 8.5.0. Users and administrators should upgrade to version 8.5.0 or later to remediate this issue. No official patch or temporary workaround is indicated in the advisory. Until upgrading, caution should be exercised regarding markdown image content from authenticated users.
CVE-2026-47733: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in RocketChat Rocket.Chat
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.
CVSS v3.1
Score 4.4medium
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Rocket.Chat before version 8.5.0 contains a CWE-79 improper input neutralization vulnerability in the ImageElement component within packages/gazzodown. Unlike the LinkSpan component, which sanitizes URLs to block dangerous protocols such as javascript:, data:, and vbscript:, ImageElement does not sanitize the protocol of user-supplied src attributes. This allows an authenticated user to craft markdown images with javascript: URLs that, if clicked on older browsers, can execute arbitrary JavaScript in the context of the viewer's session. This vulnerability has a CVSS 3.1 base score of 4.4, indicating medium severity, and is fixed in Rocket.Chat 8.5.0.
Potential Impact
An authenticated user can exploit this vulnerability to execute arbitrary JavaScript in the context of another user's session by posting a specially crafted markdown image with a javascript: URL. This could lead to limited confidentiality and integrity impacts, such as session hijacking or user interface manipulation, but does not affect availability. The attack requires user interaction (clicking the malicious link) and has a high attack complexity.
Mitigation Recommendations
This vulnerability is fixed in Rocket.Chat version 8.5.0. Users and administrators should upgrade to version 8.5.0 or later to remediate this issue. No official patch or temporary workaround is indicated in the advisory. Until upgrading, caution should be exercised regarding markdown image content from authenticated users.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-05-19T22:16:39.503Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a3c4ce24853345fc1df8d66
Added to database: 06/24/2026, 21:32:18 UTC
Last enriched: 07/01/2026, 22:40:10 UTC
Last updated: 08/09/2026, 00:41:15 UTC
Views: 81
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