wptechnitec

The rms_unique_wp_mu_pl_fl_nm.php file is part of a remote access hack.
You probably got it from a plugin download from thewordpressclub.org who include it on every plugin ( read their terms & conditions – this allows them remote access to any site with a plugin downloaded from them ) even though they say the plugin is original and untouched.
Try deleting it and it will keep re-installing itself. Until you uninstall the plugin that runs rms-script-ini.php and rms-script-mu-plugin.php when installed.
Be careful with any so-called nulled or cracked plugin. They cause more trouble than they are worth.
So FTP into your site and go through the plugins until you find the 2 files above and remove the plugin/s. Then delete the rms_unique_wp_mu_pl_fl_nm.php file, job done.

Same here had to use the following method to get front and back-end operational again…

Follow the next steps in order to delete (remove) WordPress plugin manually via FTP:

Download and install FTP client (for example, Filezilla).
Open FTP client and enter your FTP access credentials (host, username and password) to access files on your server.
Navigate to ‘yourwordpresswebsite/wp-content/plugins’ directory.
Delete (remove) necessary plugin by deleting its folder.