Got a tab in container, I went to download a file, everything was good until I removed this addon and closed Firefox. Now on every browser startup there is the same download poping up and there is no way of stopping it. EDIT: cleaning Firefox with CCleaner fixes this.
Glad you figured out a solution. What happens after removing an Add-on is completely out of control for Add-on Developers. If you encounter such Issues, your best bet might be to report them to the Firefox Bugzilla: https://bugzilla.mozilla.org/
