Rails core team reports:
This version contains three important security fixes, please upgrade immediately. One of security fixes impacts all users and is related to HTML escaping code. The other two fixes impacts people using select_tag's prompt option and strip_tags helper from ActionPack. CVE-2012-3463 Potential XSS Vulnerability in select_tag prompt. CVE-2012-3464 Potential XSS Vulnerability in the HTML escaping code. CVE-2012-3465 XSS Vulnerability in strip_tags.