The BitDefender labs came across four critical vulnerabilities affecting Winamp 5.x. Shortly thereafter, several exploits piggybacking on these vulnerabilities were spotted in the wild. The weapon used by the cyber-criminals is a malformed MTM file an audio file format similar to the MOD and MIDI file distributed to different potential victims as e-mail attachments, or through social networking or peer-to-peer file sharing. In order for the exploit to trigger its payload, it is mandatory for the user to view the file info in Winamp. This is the action that sets the exploit contained inside the malformed file into motion.”]
Source: https://www.bitdefender.com/blog/hotforsecurity/winamp-0-day-exploit-opens-backdoors/