[happymellon]

The joys of inheriting codebases is that you learn all sorts of edge cases.

Apache used to silently drop http headers with underscores in them because they state incorrectly that it is against spec, which Nginx then decided to copy in the name of "security" although it was just a flag so could be ignored if you aren't doing CGI scripting.

AWS silently added this to load balancers in 2019 until there was a backlash and they restored functionality, and then tried again to add this to API Gateways in early 2020 until, again, people complained.

HA Proxy doesn't, never did and likely never will because underscores are valid.

https://serverfault.com/questions/855720/how-to-prevent-hapr...