Cloudflare revealed a serious bug in its software today that caused sensitive data like passwords, cookies, authentication tokens to spill in plaintext from its customers’ websites. The announcement is a major blow for the content delivery network, which offers enhanced security and performance for more than 5 million websites.
This could have allowed anyone who noticed the error to collect a variety of very personal information that is typically encrypted or obscured.
Remediation was complicated by an additional wrinkle. Some of that data was automatically cached by search engines, making it particularly difficult to clean up the aftermath as Cloudflare had to approach Google, Bing, Yahoo and other search engines and ask them to manually scrub the data.
The leak may have been active as early as Sept. 22, 2016, almost five months before a security researcher at Google’s Project Zero discovered it and reported it to Cloudflare.
However, the most severe leakage occurred between Feb. 13 and Feb. 18, when around 1 in every 3,300,000 HTTP requests to Cloudflare sites would have caused data to be exposed. Attackers could have accessed the data in real-time, or later through search engine caches.
Cloudflare notes in its announcement of the issue that even at its peak, data only leaked in about 0.00003% of requests. It doesn’t sound like much, but Cloudflare’s massive customer base includes categories like dating websites and password managers, which host particularly sensitive data.