1. Create a bookmark with a tag (eg. url:"https://bugzilla.mozilla.org" tag:"bug") 2. Change the url of the bookmark (eg. url:"https://mozilla.org") > browser.bookmarks.update("e6y9yHOOv4aa",{url:"https://mozilla.org"}); 3. Open the "Library" (ctrl+shift+b) and find the "bug" tag 4. The bookmarks is not visible in the tag view 5. The tag can't be removed 6. Restore the previous address of the bookmark > browser.bookmarks.update("e6y9yHOOv4aa",{url:"https://bugzilla.mozilla.org"}); 7. Open the "Library" (ctrl+shift+b) and find the "bug" tag 8. The bookmark is visible again and you can delete the tag