Yeah, plenty of frauds made it past peer review as well, after all 

SimpleStacker

This happens a lot in other fields, like medicine.

I have mixed feelings about it. On one hand, working papers aren't nothing (they're not unlike other reporting that has no peer review) and peer review is a pretty flawed process. On the other, people probably assume things like this have undergone the heightened scrutiny of other published results.

econ

An MIT Student Awed Top Economists With His AI Study—Then It All Fell Apart

This happens a lot in other fields, like medicine.

I have mixed feelings about it. On one hand, working papers aren't nothing (they're not unlike other reporting that has no peer review) and peer review is a pretty flawed process. On the other, people probably assume things like this have undergone the heightened scrutiny of other published results.