The Smush WordPress plugin before 3.9.9 does not sanitise and escape a configuration parameter before outputting it back in an admin page when uploading a malicious preset configuration, leading to a Reflected Cross-Site Scripting. For the attack to be successful, an attacker would need an admin to upload a malicious configuration file
https://wpscan.com/vulnerability/bb5af08f-bb19-46a1-a7ac-8381f428c11e