Hi Assuming you have downloaded Firefox for Android from the Google Play Store, this should not be happening - it certainly does not happen to me. It may be the case that the sites that you are visiting have a link or a pop up that opens a page that is regarded as a threat. You may wish to look into installing a Firefox for Android add-on that may block pop-up windows. You can read more about how to do this [https://support.mozilla.org/en-US/kb/find-and-install-add-ons-firefox-android here]. I hope this helps, but if not please come back here and we can look into a different solution for you.