Popular WPForms Lite put a backdoor in their plugin

It seems like backdoor is not the right term? From that thread, as part of their setup wizard, it appears they use a 1 hour token which allows installation of additional plugins if you choose to.

If so, to use a slightly stretched analogy, it would be like an app’s setup wizard (that requires admin) allowed you (as admin) to optionally install additional items as part of the wizard (while it still has admin rights).