Origin Validation Error Affecting cinny package, versions >=0.0.0
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-JS-CINNY-16636598
- published11 May 2026
- disclosed7 May 2026
- creditQuasar0147
Introduced: 7 May 2026
NewCVE-2026-42553 (opens in a new tab)How to fix?
A fix was pushed into the master branch but not yet published.
Overview
cinny is a Yet another matrix client
Affected versions of this package are vulnerable to Origin Validation Error in the process that handles emoji pack avatar URLs in the service worker. An attacker can obtain a victim's access token by crafting a malicious emote pack with an attacker-controlled avatar URL and sharing it in a room where the victim is present. When the victim opens the emoji or sticker picker, their client sends the access token to the attacker's server via an outbound GET request containing specific Matrix media path fragments.