On m.SE last year there was a problem with someone cheating on the entrance problem set for the PRIMES high school research program at MIT. Selection for PRIMES for this year has begun, and they're taking more precautions this year to avoid this happening again. There's some things they're doing on their end, but the way these incidents are usually caught is when another user happens to recognize the problems.
So the directors of PRIMES asked me to post a link to the problem set (at meta.m.SE and here), to ask that if anyone sees any of their problems posted here that they be closed and that the moderators contact Pavel Etingof.
It's less likely that this will be a problem here at MO than at m.SE since most of their questions would get closed as off topic, but it could still come up.
Thanks, both from me and from the PRIMES directors for your help!