Tell the owners of the software to fix it.
If the actual bug is in a third party Javascript library they've got the source code so they can fix it themselves (ha ha) or replace it with something that works.
Most of the third party Javascript libraries are to some degree or other complete crap - a quick look at the code will almost always show that it's hacked together by amateurs, not designed by professional software engineers. I don't believe that Prototype is necessarily excluded from this.