Apache Struts is a free and open-source framework used to build Java web applications. Apache Struts2 S2-012 has a remote code execution vulnerability where Apache Struts Showcase App 2.0.0 through 2.3.13, as used in Struts 2 before 2.3.14.3. When a redirect is invoked, with the help of a crafted parameter, a remote attacker can execute arbitrary OGNL code.
In order to patch this vulnerability, please install the official patch made by the vendor available for supported, vulnerable instances.