XSS in Nextcloud Circles

Description

Impact

The Nextcloud Circles application was 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.

Patches

It is recommended that the Nextcloud Circles application is upgraded to 0.21.3, 0.20.10 or 0.19.14

Workarounds

Use a browser that has support for Content-Security-Policy. You can find a list of supported browsers on caniuse.com. A notable exemption is Internet Explorer which does not support CSP properly.

References

• HackerOne
• Commit

For more information

If you have any questions or comments about this advisory:

• Create a post in nextcloud/security-advisories
• Customers: Open a support ticket at support.nextcloud.com