Vnunet reports computer users have been warned to be on their guard when viewing images after the discovery of a vulnerability affecting the processing of PNG (Portable Network Graphic) files by popular applications including MSN Messenger and Windows Media Player. The issue affects applications including Windows Media Player 9.0 (when running on Windows 2000, XP Service Pack 1 and Server 2003), Windows Messenger version 5.0 (standalone version that can be installed on all supported operating systems), and MSN Messenger 6.1 and 6.2.