Something in CF updates seem to be changing the default behavior of URL encoding/decoding when making cfhttp calls. I first noticed the behavior after applying update 2 but the same breaking behavior exists in update 9 also so any update after update 1 is experiencing the problem. In the example, sender.cfm just makes a cfhttp get call to receiver.cfm where it is processed. Sender.cfm is a Windows 10 dev box running IIS 10 though I have reproduced the issue with the built in web server also.
I'm trying to identify why this occurred, whether it was a core change in CF or some other library, a CF admin setting change that I haven't been able to find, or some other config change (a jvm config file or some other instance config). Is the behavior reversible without rolling back the update.