Unlikely that a lawsuit for paysite leaks would ever happen. When an affiliate joins a program, that affiliate agrees to the Terms and Conditions which allow the program to run the site any way it sees fit. There is no contract between the program and affiliate that is broken, and thus grounds for a lawsuit, due to leaks on the join page.

The best way to deal with leaks is (1) ask for a leak-free tour (2) scream and holler for a leak-free tour or (3) only join programs with leak-free tours.
and (4) bail out from programs that add leaks to their tours.

The program does not have a contractual duty to provide a leak-free tour. But threads like this do have an effect and bring the leaks to light.