What's the exact name of that cache plugin you're using?
- If you're using LiteSpeed 5.6 or less, a cross-site scripting (XSS) vulnerability has been found in this plugin. The solution is to update it to the version 5.7.
- If you're using WP Super Cache 1.2 or less, it is vulnerable to PHP code injection. The solution is to update it to the version 1.3.2.
I recommend you to always update your plugins to their latest versions once they're released to fix vulnerabilities and other security issues. If one of them is no longer maintained / updated, please consider switching to a similar plugin.