The Easy Social Icons plugin <= 3.0.8 for WordPress echoes out the raw value of `$_SERVER['PHP_SELF']` in its main file. On certain configurations including Apache+modPHP this makes it possible to use it to perform a reflected Cross-Site Scripting attack by injecting malicious code in the request path.
https://www.wordfence.com/vulnerability-advisories/#CVE-2021-39322
https://wpvulndb.com/vulnerabilities/5e0bf0b6-9809-426b-b1d4-1fb653083b58