HTML injection in search results via plaintext message highlighting
Date: 2023-04
Affected: npm/matrix-react-sdk
Attack vector: xss
Category: vulnerability-disclosure
Severity: High
CVE: CVE-2023-30609
CWE: CWE-74
CWE-79
CVSS: 8.2 (CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:L)

### Impact Plain text messages containing HTML tags are rendered as HTML in the search results. To exploit this, an attacker needs to trick a user into searching for a specific message containing an HTML injection payload. Cross-site scripting is possible by including resources from `recaptcha.net` and `gstatic.com` which are included in the default CSP. Thanks to [Cadence Ember](https://cadence.moe/) for finding the injection and to [S1m](https://github.com/p1gp1g/) for finding possible XSS vectors. ### Patches Version 3.71.0 of the SDK fixes the issue. ### Workarounds Restarting the client will clear the injection.


Mitigations:

Architectural layers (MAESTRO):