Input validation vulnerability in Simple Membership 4.6.3

The Simple Membership plugin for WordPress has a security flaw that could allow hackers to inject harmful code into web pages. This can happen in versions up to 4.6.3 because the plugin does not properly clean up user input. If a hacker with high-level access to the site adds malicious code, it could run whenever a user visits the affected page. This only affects websites with multiple installations and those that have disabled certain security measures.