WordPress InfiniteWP Client Authentication Bypass

This module exploits an authentication bypass in the WordPress
InfiniteWP Client plugin to log in as an administrator and execute
arbitrary PHP code by overwriting the file specified by PLUGIN_FILE.

The module will attempt to retrieve the original PLUGIN_FILE contents
and restore them after payload execution. If VerifyContents is set,
which is the default setting, the module will check to see if the
restored contents match the original.

Note that a valid administrator username is required for this module.

WordPress >= 4.9 is currently not supported due to a breaking WordPress
API change. Tested against 4.8.3.