iceweasel-ublock-origin software package provides virtual package provided by xul-ext-ublock-origin, you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install iceweasel-ublock-origin
iceweasel-ublock-origin is installed in your system.
Make ensure the iceweasel-ublock-origin package were installed using the commands given below,
$ sudo dpkg-query -l | grep iceweasel-ublock-origin*
You will get with iceweasel-ublock-origin package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Virtual packages |
| Package | iceweasel-ublock-origin |
| Version | |
| Description | virtual package provided by xul-ext-ublock-origin |
| Sub Section | Virtual |