Mozilla Firefox before 1.5.0.1, Thunderbird 1.5 if running Javascript in mail, and SeaMonkey before 1.0 allow remote attackers to execute arbitrary code by changing an element's style from position:relative to position:static, which causes Gecko to operate on freed memory.
The Javascript interpreter (jsinterp.c) in Mozilla and Firefox before 1.5.1 does not properly dereference objects, which allows remote attackers to cause a denial of service (crash) or execute arbitrary code via unknown attack vectors related to garbage collection.
run-mozilla.sh in Thunderbird, with debugging enabled, allows local users to create or overwrite arbitrary files via a symlink attack on temporary files.