Gitea's OAuth2 token endpoint verified the signature and grant of a token submitted with the `refresh_token` grant type, but not that the token was a refresh token. An unexpired access token for the same OAuth2 application and grant could be exchanged for a new access token and refresh token. Whoever holds such an access token could keep access beyond the token's original lifetime.
https://github.com/go-gitea/gitea/security/advisories/GHSA-469m-x4mw-38r3
https://github.com/go-gitea/gitea/releases/tag/v28.1.0
https://github.com/go-gitea/gitea/pull/39507
https://github.com/go-gitea/gitea/pull/39501