Multiple vulnerabilities has been discovered and corrected in
squirrelmail:

functions/page_header.php in SquirrelMail 1.4.21 and earlier does not
prevent page rendering inside a frame in a third-party HTML document,
which makes it easier for remote attackers to conduct clickjacking
attacks via a crafted web site (CVE-2010-4554).

Multiple cross-site scripting (XSS) vulnerabilities in SquirrelMail
1.4.21 and earlier allow remote attackers to inject arbitrary
web script or HTML via vectors involving (1) drop-down selection
lists, (2) the > (greater than) character in the SquirrelSpell
spellchecking plugin, and (3) errors associated with the Index Order
(aka options_order) page (CVE-2010-4555).

Cross-site scripting (XSS) vulnerability in functions/mime.php in
SquirrelMail before 1.4.22 allows remote attackers to inject arbitrary
web script or HTML via a crafted STYLE element in an e-mail message
(CVE-2011-2023).

CRLF injection vulnerability in SquirrelMail 1.4.21 and earlier
allows remote attackers to modify or add preference values via a n
(newline) character, a different vulnerability than CVE-2010-4555
(CVE-2011-2752).

Multiple cross-site request forgery (CSRF) vulnerabilities in
SquirrelMail 1.4.21 and earlier allow remote attackers to hijack the
authentication of unspecified victims via vectors involving (1) the
empty trash implementation and (2) the Index Order (aka options_order)
page, a different issue than CVE-2010-4555 (CVE-2011-2753).

The updated packages have been upgraded to the 1.4.22 version which
is not vulnerable to these issues.