CVE 2010-1401
Use-after-free vulnerability in the Cascading Style Sheets (CSS) implementation in WebKit in Apple Safari before 5.0 on Mac OS X 10.5 through 10.6 and Windows, and before 4.1 on Mac OS X 10.4, allows remote attackers to execute arbitrary code or cause a denial of service (application crash) via vectors involving the :first-letter pseudo-element.
See the 
CVE page on Mitre.org
for more details.
