Mantis Bug Tracker (MantisBT) is an open source issue tracker. Versions prior to 2.28.1 running on MySQL family databases are affected by an authentication bypass vulnerability in the SOAP API, as a result of an improper type checking on the password parameter. Other database backends are not affected, as they do not perform implicit type conversion from string to integer. Using a crafted SOAP envelope, an attacker knowing the victim's username is able to login to the SOAP API with their account without knowledge of the actual password, and execute any API function they have access to. Version 2.28.1 contains a patch. Disabling the SOAP API significantly reduces the risk, but still allows the attacker to retrieve user account information including email address and real name.