Prominent blockchain security firm CertiK has accused American cryptocurrency exchange Kraken of threatening them after they reported a bug. According to CertiK, they discovered a bug in the exchange software, which they tested with multiple transactions over several days. Some of these were large transactions, which CertiK said they performed to test whether Kraken had alerting in place to detect higher-value transfers. When they reported the vulnerability to the exchange, they say the exchange patched the bug, but then threatened CertiK employees and demanded they repay a "mismatched" amount of crypto allegedly taken during the testing period.However, others have noted that the number of transactions and amount of cryptocurrency taken by CertiK while "investigating" the bug seems to far exceed the norm for whitehat security researchers, and that they took cryptocurrency amounting to millions of dollars — making their "testing" look a lot more like a blackhat theft. Furthermore, CertiK made several transfers to Tornado Cash as part of their "testing" — an entity that is sanctioned by the United States.
Kraken alleged that CertiK did not disclose the full extent of their employees' transactions, and refused to return the $3 million they had taken. They also alleged that CertiK had attempted to extort them. Kraken said they had been in contact with law enforcement, and were "treating this as a criminal case".
Ultimately, CertiK returned the funds. However, it's not clear if criminal action may be ongoing.