The most common implementation of this appears to be from a company called Bytemobile which also injects some pretty buggy JavaScript into HTML content.
The good news is that you can disable all of their degradation by adding "no-transform" to your Cache-Control headers:
“The standard HTTP header Cache-Control: no-transform which tells proxies not to modify responses was respected by all proxies I've encountered. This is amazing! It wins an award in the "Best Supported Obscure Header" category.”
The good news is that you can disable all of their degradation by adding "no-transform" to your Cache-Control headers:
https://kornel.ski/en/proxies
“The standard HTTP header Cache-Control: no-transform which tells proxies not to modify responses was respected by all proxies I've encountered. This is amazing! It wins an award in the "Best Supported Obscure Header" category.”