There have been claims that the flaw could be exploited by hackers to install malicious software onto vulnerable machines.
According to these claims the flaw could be used by .wav, .snd and .mid audio files to compromise the computer if it is running Windows XP or Vista.
This problem is said to affect Windows Media Player versions 9, 10 and 11, but Microsoft have disputed that the flaw means serious problems.
It says that it cannot affect the security of the machine, but could mean that the media player will crash and then have to be restarted.
However, Microsoft is yet to issue a fix for this problem.