In an approach for testing an application for a security vulnerability, a processor inserts an instrumentation hook in the application to be tested, wherein the instrumentation hook is executed prior to a sink operation. A processor transmits a probe input value to the application to be tested. A processor detects a modification to the probe input value at the instrumentation hook by comparing the probe input value at the instrumentation hook to a signature value and detecting that the probe input value matches the signature value. A processor removes the sink operation from testing for the security vulnerability.