Tvheadend

Don't know exactly on a MOI - it depends on whether you have privileged (root or hts) access to the command line. If you do, navigate to your config directory and look in the accesscontrol directory - that lists the access rules, one per file, each containing username and password details, so you can edit/delete them here. You also have a superuser file that contains the master user credentials in plain text. Try one of those.