The Validator in Apache Struts 1.1 and later contains a function to efficiently define rules for input validation across multiple pages during screen transitions. This function contains a vulnerability where input validation may be bypassed. When the Apache Struts 1 Validator is used, the web application may be vulnerable even when this function is not used explicitly. (CVE-2015-0899)
Impact
An attacker may be able to skip input validation when the vulnerability is exploited.