Symantec has issued a security warning to users of the RealPlayer media software after discovering attack code that can enable a back door exploit on vulnerable Windows computers. The Windows XP SP1 RealPlayer 11 beta and RealPlayer 10.5 versions are affected when run with Internet Explorer 6. The suspicious code was given to Symantec by a customer in the US. Users can minimize the threat by disabling JavaScript and ActiveX. According to Symantec, the malicious code would need to be re-written to deliver the same exploit on the Macintosh and Linux platforms. RealNetworks, the manufacturer of RealPlayer, has not yet released a security update for the vulnerability.