An issue was discovered in MantisBT before 2.24.5. It associates a unique cookie string with each user. This string is not reset upon logout (i.e., the user session is still considered valid and active), allowing an attacker who somehow gained access to a user's cookie to login as them.

MantisBT before 1.2.12 does not use an expected default value during decisions about whether a user may modify the status of a bug, which allows remote authenticated users to bypass intended access restrictions and make status changes by leveraging a blank value for a per-status setting.