Since many users lets their browsers play music etc automatically...

Secunia writes:
QUOTE
Description:
Two vulnerabilities have been reported in various RealNetworks products, which can be exploited by malicious people to compromise a user's system.

1) A boundary error within the processing of WAV files can be exploited to cause a buffer overflow via a specially crafted WAV file.

2) A boundary error within the processing of SMIL files can be exploited to cause a stack-based buffer overflow via a specially crafted SMIL file.

Successful exploitation of the vulnerabilities allows execution of arbitrary code.

Solution:
Apply patches.

RealOne / RealPlayer for Windows and Mac:
Patches are available via the "Check for Update" feature.

RealPlayer Enterprise:
http://service.real.com/help/faq/security/...rity022405.html

Linux Players:
RealPlayer 10:
http://www.real.com/linux

Helix Player:
http://player.helixcommunity.org/downloads/