Groove Virtual Office before 3.1 build 2338, before 3.1a build 2364, and Groove Workspace before 2.5n build 1871 does not properly display file extensions on attached or embedded files in a compound document, which may allow remote attackers to trick users into executing malicious code.
http://www.kb.cert.org/vuls/id/JGEI-6BCRD6