Relevanssi has a search function on the admin side that is not visible in the user interface, however the code is there and can be called. This functionality contains an sql injection, and this sql injection can be exploited to pass user controlled values into an unserialization call and run arbitrary code (if there are classes available with particular methods such as
Proof of concept
Achieving arbitrary code execution depends on which classes are available (i.e. which plugins and themes are installed and active). It won’t be possible in all situations.
Upgrade to version 126.96.36.199 or later.