The Linux install .tar.gz archives for Mozilla Firefox before the Preview Release, Mozilla before 1.7.3, and Thunderbird before 0.8, create certain files with insecure permissions, which could allow local users to overwrite those files and execute arbitrary code.
https://exchange.xforce.ibmcloud.com/vulnerabilities/17373
http://www.mozilla.org/projects/security/known-vulnerabilities.html#mozilla1.7.3