This advisory announces two security vulnerabilities that were found in Jenkins core.
The first vulnerability is commonly known as HTTP response splitting vulnerability, which can act as a cross-site scripting vulnerability. This allows an anonymous attacker to inject malicious HTMLs to pages served by Jenkins. This in turn allows an attacker to escalate his privileges by hijacking sessions of other users. To mount this attack, the attacker needs to know the exact URL of your Jenkins installation. This vulnerability affects those who run Jenkins on its built-in servlet container (this includes all the native packages.)
The second vulnerability is so-called open redirect vulnerability. This allows an anonymous attacker to create an URL that looks as if it's pointing to Jenkins, yet it actually lands on the site that the attacker controls. This can be therefore used as a basis for phishing.
These vulnerabilities are discovered by Soroush Dalili , and we'd like to thank him.