The maintainers of the open-source SquirrelMail webmail package is warning of a compromise that could introduce a "high risk" security issue on end-user servers.
The package compromise, which affects SquirrelMail 1.4.11 and 1.4.12, was discovered when the MD5 sums for the 1.4.12 package were not matching the actual package. An initial investigation found that it was caused by a breached account from a release maintainer and caused the package to be modified post release.
A note on the SquirrelMail home page sounds the alarm:
While initial review didn't uncover a need for concern, several proof of concepts show that the package alterations introduce a high risk security issue, allowing remote inclusion of files. These changes would allow a remote user the ability to execute exploit code on a victim machine, without any user interaction on the victim's server. This could grant the attacker the ability to deploy further code on the victim's server.
The group is strongly advising users to upgrade to version 1.4.13 immediately.