Description
This script is using the PHP function preg_replace() on user input. This is not recommended as it can lead to various vulnerabilities. Consult "Web references" for more information about this problem.
The e modifier makes preg_replace() treat the replacement parameter as PHP code after the appropriate references substitution is done. If the regex pattern and the replacement strings are controlled by the user this can conduct to PHP code execution.
Remediation
It is not recommended to use preg_replace() on user input.
References
Related Vulnerabilities
Unauthenticated remote code execution vulnerability in Confluence Server and Data Center
Same origin method execution (SOME)
WordPress 'wp-admin/options.php' Remote Code Execution Vulnerability (0.6.2 - 2.3.2)
WordPress Plugin ProfileGrid-User Profiles, Groups and Communities Remote Code Execution (2.8.5)