Hi, we are getting a lot of reports like yours of late - it's a scam designed to infect you with malware! NEVER EVER click on anything like that.

If you are in any doubt about the authenticity of update pop-ups etc., it's always best to ignore them and check for yourself by opening the 3-bar menu > Help (question mark at bottom right) > About Firefox. Alternatively, you can press the Alt key to bring up the main menu bar > Help > About Firefox. More - Update Firefox to the latest release.

For reference only - please don't post here - this forum is for Mozilla Support Contributors only. https://support.mozilla.org/en-US/forums/contributors/712056?last=69507

If your question is resolved by this or another answer, please take a minute to let us know. Thank you.

Thanks, I thought it sounded phony. I'll keep deleting them.

Hi Ploughboy, is there any pattern to the pages you visited just before this unwanted tab opens? The prevailing thinking is that an ad network is spreading them on popular sites.

Haven't noticed anything obvious but wasn't really looking. I'll pay more attention from now on to see if there is a pattern.