A special directory in WordPress, called mu-plugins, has been abused by threat actors to host malicious code.
The malicious code in mu-plugins allows threat actors to execute arbitrary code, redirect visitors to malicious websites, and display spam and ads.
Sucuri researchers found three variants of malicious code in mu-plugins, including redirect.php, index.php, and custom-js-loader.php.
To mitigate the risk, website admins should conduct regular security checks, scan for malicious files, update plugins and themes, and monitor file integrity.