Bitcoins may be traded on Exchange Services for traditional currencies, such as EUR, USD, GBP, etc. This require combining Bitcoin wallets with mobile payment gateways, which are not 100% secure. McCorry, Shahandashti and Hao presented two Refund attacks referred as, Silkroad trader attack and Marketplace trader attack, on BIP70 that exploits the one-way authentication of the protocol.

Paper:

McCorry, P., Shahandashti, S.F., Hao, F.: Refund attacks on bitcoins payment protocol. In: International Conference on Financial Cryptography and Data Security. pp. 581–599. Springer (2016)