Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:59.0) Gecko/20100101 Firefox/59.0 20171206221407 1. Start Nightly in a brand new profile. 2. Install the latest uBlock Origin, currently 1.14.20. 3. On the My Filters tab, enter a large number of filters (a little over 100 does it in my case), then click the Apply button when done. The actual filters themselves are irrelevant; I just used 101 instances of "! just a comment". 4. Click in the middle of one of your filters. 5. Press any of the arrow keys. Actual results: The moment you click in the middle of the text on the My Filters tab, the caret (text cursor) stops blinking. It doesn't move when the arrow keys are pressed. This doesn't happen when clicking outside of text, i.e. the empty lines below the custom filters. It seems the more filters, the more sluggish the caret response becomes. In my testing, it was fine with 90 filters but became unusable past 100. Expected results: The caret moves as the arrow keys are pressed or text is typed.

I get a similar behavior when editing long textarea on GitHub. For example, if you have a GitHub account, open the following link (don't save changes, just move the cursor around) : https://github.com/gorhill/uMatrix/wiki/Per-scope-switches/_edit Then move the cursor to the end of the text (ctrl-end): the cursor response become sluggish. This happens pretty systematically, whenever the amount of text in a textarea beyond a certain length. Given this, I think the severity should be re-assessed.

Maybe, WebExtension's IPC use invalid widget like bug 1419285

Duplicate? Bug 1427531

Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:61.0) Gecko/20100101 Firefox/61.0 20180326132207 (In reply to Gingerbread Man from comment #0) > 2. Install the latest uBlock Origin, currently 1.14.20. Fixed in uBlock Origin, as far as I can tell. I can no longer reproduce the issue with the latest version. It was presumably fixed in version 1.15.14, which is when the editor changed. That being said, I can reproduce something virtually identical to comment 1 in a brand new profile with no add-ons. Therefore, I've confirmed bug 1448818.