Nextcloud Talk is an open source chat, video & audio calls client for the Nextcloud platform. In affected versions an attacker could see the last video frame of any participant who has video disabled but a camera selected. It is recommended that the Nextcloud Talk app is upgraded to 13.0.8 or 14.0.4. Users unable to upgrade should select "None" as camera before joining the call.
https://github.com/nextcloud/spreed/pull/7673
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-wq3g-2x46-q2gv