Security issues were identified and fixed in mozilla firefox and
thunderbird:

Mozilla Firefox before 3.6.23 and 4.x through 6, Thunderbird before
7.0, and SeaMonkey before 2.4 do not prevent the starting of a download
in response to the holding of the Enter key, which allows user-assisted
remote attackers to bypass intended access restrictions via a crafted
web site (CVE-2011-2372).

Multiple unspecified vulnerabilities in the browser engine in Mozilla
Firefox before 3.6.23 and 4.x through 6, Thunderbird before 7.0,
and SeaMonkey before 2.4 allow remote attackers to cause a denial of
service (memory corruption and application crash) or possibly execute
arbitrary code via unknown vectors (CVE-2011-2995).

Multiple unspecified vulnerabilities in the browser engine in Mozilla
Firefox 6, Thunderbird before 7.0, and SeaMonkey before 2.4 allow
remote attackers to cause a denial of service (memory corruption and
application crash) or possibly execute arbitrary code via unknown
vectors (CVE-2011-2997).

Mozilla Firefox before 3.6.23 and 4.x through 6, Thunderbird before
7.0, and SeaMonkey before 2.4 do not properly handle HTTP responses
that contain multiple Location, Content-Length, or Content-Disposition
headers, which makes it easier for remote attackers to conduct HTTP
response splitting attacks via crafted header values (CVE-2011-3000).

Mozilla Firefox 4.x through 6, Thunderbird before 7.0, and SeaMonkey
before 2.4 do not prevent manual add-on installation in response
to the holding of the Enter key, which allows user-assisted remote
attackers to bypass intended access restrictions via a crafted web
site that triggers an unspecified internal error (CVE-2011-3001).

Use-after-free vulnerability in Mozilla Firefox 4.x through 6,
Thunderbird before 7.0, and SeaMonkey before 2.4 allows remote
attackers to cause a denial of service (application crash) or
possibly execute arbitrary code via crafted OGG headers in a .ogg file
(CVE-2011-3005).

YARR, as used in Mozilla Firefox before 7.0, Thunderbird before 7.0,
and SeaMonkey before 2.4, allows remote attackers to cause a denial
of service (application crash) or possibly execute arbitrary code
via crafted JavaScript (CVE-2011-3232).