functions/mime.php in SquirrelMail before 1.4.18 does not protect the application's content from Cascading Style Sheets (CSS) positioning in HTML e-mail messages, which allows remote attackers to spoof the user interface, and conduct cross-site scripting (XSS) and phishing attacks, via a crafted message.
https://www.redhat.com/archives/fedora-package-announce/2009-May/msg00577.html
https://www.redhat.com/archives/fedora-package-announce/2009-May/msg00572.html
https://www.redhat.com/archives/fedora-package-announce/2009-May/msg00566.html
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A10441
https://exchange.xforce.ibmcloud.com/vulnerabilities/50463
https://bugzilla.redhat.com/show_bug.cgi?id=500356
http://www.vupen.com/english/advisories/2010/1481
http://www.vupen.com/english/advisories/2009/1296
http://www.squirrelmail.org/security/issue/2009-05-12
http://www.securityfocus.com/bid/34916
http://www.redhat.com/support/errata/RHSA-2009-1066.html
http://www.mandriva.com/security/advisories?name=MDVSA-2009:110
http://www.debian.org/security/2009/dsa-1802
http://support.apple.com/kb/HT4188
http://squirrelmail.svn.sourceforge.net/viewvc/squirrelmail?view=rev&revision=13667
http://secunia.com/advisories/40220
http://secunia.com/advisories/35259
http://secunia.com/advisories/35140
http://secunia.com/advisories/35073
http://secunia.com/advisories/35052
http://lists.apple.com/archives/security-announce/2010//Jun/msg00001.html