A threat advisory paper by information security firm Command Five has made the claim that Atlassian may be including a backdoor in its Crowd software.
The paper in question (PDF) focuses on an XML parsing vulnerability in Crowd, designated by the CVE identifier CVE-2013-3925. This vulnerability allows an attacker to do things like remotely retrieve files from the network or conduct denial-of-service attacks, but it has since been patched.
However, the paper also highlights another, yet unreported, vulnerability: CVE-2013-3926. According to Command Five, it allows a remote attacker to “take full control of any Crowd server to which they are able to make a network connection”. Unlike an accidental vulnerability, though, the paper said that it is covertly positioned, needs of the use of special parameters, leaves no log messages, and has the ability to persist once exploited.