Mt. Gox, once the world's largest Bitcoin exchange, collapsed in February 2014 after announcing the loss of approximately 850,000 BTC (then ~$450M; worth billions at later prices). CEO Mark Karpelès initially claimed transaction malleability attacks were responsible. Independent blockchain forensics firm WizSec attributed the losses to systematic key theft beginning in 2011. Karpelès was convicted in March 2019 for data falsification — not theft. Alexander Vinnik, operator of BTC-e (a money laundering exchange), was indicted in 2017 for receiving proceeds of the Mt. Gox theft. The true mechanism remains partially contested.