Cross-Site Scripting in Nextcloud Circles

Vulnerability Description

Nextcloud Circles is an open source social network built for the nextcloud ecosystem. In affected versions the Nextcloud Circles application is vulnerable to a stored Cross-Site Scripting (XSS) vulnerability. Due the strict Content-Security-Policy shipped with Nextcloud, this issue is not exploitable on modern browsers supporting Content-Security-Policy. It is recommended that the Nextcloud Circles application is upgraded to 0.21.3, 0.20.10 or 0.19.14 to resolve this issue. As a workaround users may use a browser that has support for Content-Security-Policy. A notable exemption is Internet Explorer which does not support CSP properly.

References

• https://github.com/nextcloud/security-advisories/security/advisories/GHSA-hgpq-28gj-jrj9
• https://github.com/nextcloud/circles/commit/dbb97a83ccb342c839a54f088aa19b8ba6844b0e
• https://hackerone.com/reports/1217606