Bamboo before 6.0.5, 6.1.x before 6.1.4, and 6.2.x before 6.2.1 had a REST endpoint that parsed a YAML file and did not sufficiently restrict which classes could be loaded. An attacker who can log in to Bamboo as a user is able to exploit this vulnerability to execute Java code of their choice on systems that have vulnerable versions of Bamboo.