options_identities.php in SquirrelMail 1.4.4 and earlier uses the extract function to process the $_POST variable, which allows remote attackers to modify or read the preferences of other users, conduct cross-site scripting XSS) attacks, and write arbitrary files.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A10500
https://exchange.xforce.ibmcloud.com/vulnerabilities/21359
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=163047
http://www.squirrelmail.org/security/issue/2005-07-13
http://www.securityfocus.com/bid/14254
http://www.securityfocus.com/archive/1/405202
http://www.securityfocus.com/archive/1/405200
http://www.redhat.com/support/errata/RHSA-2005-595.html
http://www.novell.com/linux/security/advisories/2005_18_sr.html
http://www.gulftech.org/?node=research&article_id=00090-07142005
http://www.debian.org/security/2005/dsa-756
http://lists.apple.com/archives/security-announce/2005/Aug/msg00000.html
http://lists.apple.com/archives/security-announce/2005//Aug/msg00001.html