user_oidc app is an OpenID Connect user backend for Nextcloud. An attacker could potentially trick the app into accepting a request that is not signed by the correct server. It is recommended that the Nextcloud user_oidc app is upgraded to 1.3.5, 2.0.0, 3.0.0, 4.0.0 or 5.0.0.
https://hackerone.com/reports/1878391
https://github.com/nextcloud/user_oidc/pull/715
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-vw5h-29xf-g55g