Comment by tannhaeuser
8 years ago
From https://arstechnica.com/security/2017/02/serious-cloudflare-...:
A while later, we figured out how to reproduce
the problem. It looked like that if an html page
hosted behind cloudflare had a specific
combination of unbalanced tags,
[...]
The leakage was the result of a bug in an HTML
parser chain Cloudflare uses to modify Web pages
as they pass through the service's edge servers.
Ahem, at the risk of sounding pedantic, but this wouldn't have happened when using a proper HTML/SGML parser ([1]).