The WeTransfer file sharing service was sending users shared files to the wrong people on June 16th and 17th. The service is used to transfer what are considered private, and potentially sensitive files. WeTransfer posted a security notice on their web site that some accounts were logged out and had their passwords reset to protect their accounts. As a precaution, WeTransfer blocked access to the Transfer links that were involved in the incident. BleepingComputer has contacted WeTransfer about this incident but had not heard back.
Source: https://www.bleepingcomputer.com/news/security/wetransfer-security-incident-sent-files-to-the-wrong-people/