A little risky though, if your test is imperfect. People may work to outsmart the tests rather than actually solve the bugs.

Yes, I was going to add a note on that but then I realized this problem (people cheating) would exist anyways as long as there isn't a trusted third party to handle conflicts. I don't think this would be a common issue though as most open source developers are not driven by the money and I don't think there would be enough money to attract scammers (would someone really get into the trouble of writing an open source software hoping to one day cheat people out of their money when they submit bug bounties?).