In Gitea before 1.16.9, it was possible for users to add existing issues to projects. Due to improper access controls, an attacker could assign any issue to any project in Gitea (there was no permission check for fetching the issue). As a result, the attacker would get access to private issue titles.
An issue exsits in Gitea through 1.15.7, which could let a malicious user gain privileges due to client side cookies not being deleted and the session remains valid on the server side for reuse.