CVE 2009-1689
Cross-site scripting (XSS) vulnerability in WebKit in Apple Safari before 4.0, iPhone OS 1.0 through 2.2.1, and iPhone OS for iPod touch 1.1 through 2.2.1 allows remote attackers to inject arbitrary web script or HTML via vectors involving submission of a form to the about:blank URL, leading to security-context replacement.
See the 
CVE page on Mitre.org
for more details.
