Users of Pidgin and other alternative IM clients need to update their software following the discovery of potentially serious security flaws.

Pidgin, Finch, Adium, Meebo, and Gaim are all vulnerable to a flaw that stems from a bug in Libpurple, library software for multi-protocol support that's used by many IM clients. The vulnerability stems from bugs in the software function that handles instant messages from the MSN network. The flaw was discovered by CORE Security whose advisory can be found here.

The flaw is particularly serious because all it takes to take advantage of the vulnerability is a message from a regular MSN user, not necessarily on a targeted user's buddy list, the SANS Institute Internet Storm Centre warns.

Users are advised to update to an IM client that uses non-vulnerable versions of Libpurple (version 2.5.9 or above). For Pidgin, the most common of the alternative IM packages affected, that means updating to version 2.5.9 as explained here.

The issue provides further evidence that users of alternative client software may remove themselves from the main line of attacks but not from the need to patch their systems. ®