XSS in Talk

Description

Impact

The Nextcloud Talk application was vulnerable to a stored Cross-Site Scripting (XSS) vulnerability. For exploitation, a user would need to right-click on a malicious file and open the file in a new tab.

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 Talk application is upgraded to 10.0.7, 10.1.4, 11.1.2, 11.2.0 or 12.0.0.

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
• Pull Request

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