Cloudflare is a company that provides a content delivery network (CDN) to lots and lots of sites. A software bug was discovered that potentially rendered cached user names and passwords to lots and lots of sites… vulnerable.
- Here’s one write-up.
- Here’s another write-up.
- Here’s the official write-up.
- Here’s an unofficial list of domains impacted by the bug.
The short of it – you may want to do a crosscheck of domains against your user accounts, & consider updating passwords.