Furthermore, files could have been placed in the account that appear to have been uploaded by the account holder (a “framing” attack). Files in the cloud drive could have been successively decrypted during subsequent logins. Once a targeted account had made enough successful logins, incoming shared folders, MEGAdrop files and chats could have been decryptable. Very few: An attacker would have had to first gain control over the heart of MEGA’s server infrastructure or achieve a successful man-in-the-middle attack on the user’s TLS connection to MEGA. Who could have exploited the vulnerability? While all MEGA client products use permanent sessions by default, some third-party clients such as Rclone do not.

Note that resuming an existing session does not count as a login. They also confirmed that “he patches that MEGA developed to mitigate the original key recovery attack are effective against our improved attack as well, so updated clients are not vulnerable to the techniques presented in this work.” Update: On 14 July 2022, the University of California San Diego published additional research that reduced that threshold to just six. The ETH Zurich exploit required customers to log into their MEGA account at least 512 times (the more, the higher the exposure). Further updates addressing less severe identified issues will follow in the near future. MEGA is not aware of any user accounts being compromised by these vulnerabilities. Today, MEGA has released software updates that fix a critical vulnerability reported by researchers at one of Europe’s leading universities, ETH Zurich, Switzerland.

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