A vulnerability in Firefox for Android paves the way for an attackers to launch websites on a victim s phone, with no user interaction. The attack manifests in the form of a Firefox browser window on the target device suddenly launching, without the users permission. To exploit the bug, an attacker would need to be attached to the same Wi-Fi network as the target, according to researcher Chris Moberly. Firefox users should update their application to version 79 or 79 (this may have already been done)
Source: https://threatpost.com/firefox-android-bug-rick-rolling/159397/