Fullscreen could be enabled without displaying the security UI
CVE: CVE-2020-26953
Component: Mozilla
CWE: CWE-451
Severity: Moderate
CVSS v3: 4.2/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
Release date: 2020-11-17T00:00:00+00:00

It was possible to cause the browser to enter fullscreen mode without displaying the security UI; thus making it possible to attempt a phishing attack or otherwise confuse the user. This vulnerability affects Firefox < 83, Firefox ESR < 78.5, and Thunderbird < 78.5.


Remediation:
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

After installing the update, Firefox must be restarted for the changes to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

All running instances of Thunderbird must be restarted for the update to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

After installing the update, Firefox must be restarted for the changes to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

All running instances of Thunderbird must be restarted for the update to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

After installing the update, Firefox must be restarted for the changes to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

All running instances of Thunderbird must be restarted for the update to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

After installing the update, Firefox must be restarted for the changes to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

All running instances of Thunderbird must be restarted for the update to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

After installing the update, Firefox must be restarted for the changes to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

All running instances of Thunderbird must be restarted for the update to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

After installing the update, Firefox must be restarted for the changes to take effect.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

All running instances of Thunderbird must be restarted for the update to take effect.