CVE-2021-23984

Name of the Vulnerable Software and Affected Versions Firefox ESR versions prior to 78.9 Firefox versions prior to 87 Thunderbird versions prior to 78.9

Description A malicious extension could open a popup window lacking an address bar, with a fully controllable title, allowing it to spoof a website and attempt to trick the user into providing credentials. This issue is related to incorrect restriction of visualizable layers or frames in the user interface, which could enable a remote attacker to conduct spoofing attacks.

Recommendations For Firefox ESR versions prior to 78.9, update to version 78.9 or later. For Firefox versions prior to 87, update to version 87 or later. For Thunderbird versions prior to 78.9, update to version 78.9 or later.