A backdoor in xz

In retrospect, I think most people would agree that the design of PAM was a mistake. It was hugely controversial at its time and many fought against its inclusion in distributions.

In the end it was included because it made possible some use cases where no one else stepped up to make a practical alternative.

I don't think that is something we want to emulate. It is certainly possible to satisfy the necessary use cases without resorting to dlopen().