Include the X-Forwarded-Proto header when acting as an HTTPS proxy
There are many situations where a Web application needs to know whether the original connection was made over HTTPS or HTTP. Typically, SSL proxies communicate this by inserting the X-Forwarded-Proto header into the request. Currently, the ASG only adds the following headers:
Micha Lenk commented
This should be already available with UTM 9.1 (or even earlier).