The version of the bundled Atlassian OAuth plugin was vulnerable to Server Side Request Forgery (SSRF). This allowed a XSS and or a SSRF attack to be performed. More information about the Atlassian OAuth plugin issue see https://ecosystem.atlassian.net/browse/OAUTH-344 . When running in an environment like Amazon EC2, this flaw can used to access to a metadata resource that provides access credentials and other potentially confidential information.