Several security vulnerabilities have been disclosed by Monero, including one that could have been exploited to steal xmr from exchanges
Source: https://cointelegraph.com/news/monero-discloses-bug-allowing-xmr-to-be-stolen-from-exchanges
Monero Discloses Bug Allowing XMR to be Stolen from Exchanges
July 5, 2019
CoinTelegraph