Telerik Fiddler through 5.0.20202.18177 allows attackers to execute arbitrary programs via a hostname with a trailing space character, followed by --utility-and-browser --utility-cmd-prefix= and the pathname of a locally installed program. The victim must interactively choose the Open On Browser option. Fixed in version 5.0.20204.
https://www.telerik.com/support/whats-new/release-history
https://www.telerik.com/support/whats-new/fiddler/release-history/fiddler-v5.0.20204