Group-Office is an enterprise customer relationship management and groupware tool. Versions prior to 26.0.9, 25.0.87, and 6.8.154 have an authenticated Remote Code Execution vulnerability in the TNEF attachment processing flow. The vulnerable path extracts attacker-controlled files from winmail.dat and then invokes zip with a shell wildcard (*). Because extracted filenames are attacker-controlled, they can be interpreted as zip options and lead to arbitrary command execution. Versions 26.0.9, 25.0.87, and 6.8.154 fix the issue.