BNT Liquidity Mining Audit by Peckshield here (February, 2021)
Bancor v2.1 audit by Peckshield here. (October, 2020)
Bancor v2 audit by Halborn here (August, 2020)
Bancor v2 audit by Consensys Due Diligence here. (July, 2020)
Bancor v1 audit can be found here. (May, 2017)
Bancor has an open and ongoing bug bounty program.