Security is paramount to us, so we are offering $500 per critical flaw discovered in metaexchange. Either through the analysis of the source code, or through direct reproducible action.
Critical flaw is defined as any exploitable hole where an attacker can gain access to funds outside of the designed system. An example would be some edge case which causes multiple refunds to be issued for the same transaction, or a route through which an attacker could access special admin commands.
If you're interested in doing this analysis, shoot me a PM and I will give you all the locations in the code base which will be of interest.