Requesting a user or organization profile page (`GET /{username}`) with an `Accept: application/rss+xml` or `Accept: application/atom+xml` header returned the owner's activity feed without the visibility check that the profile page and the `.rss` and `.atom` routes apply. Anonymous users, restricted users and non-members could confirm the existence of limited or private users and private organizations and read their profile details and public activity, also when `[other] ENABLE_FEED` was disabled. Activity in private repositories was not included.
https://github.com/go-gitea/gitea/security/advisories/GHSA-hf55-9cwq-2x64
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