icm/accept_forwarded_cert_via_http is a SAP Parameter attribute which is used to control Accept X.509 client certificate that was forwarded via HTTP information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
This parameter specifies if the ICM accepts a client-certificate that
was forwarded via HTTP (not HTTPS).
This removes the trust relationship and the associated security measures
(deletion of header fields). Only set this parameter to TRUE after
carefully considering the security risks.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.