Description
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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mozilla | Firefox | < 83 | — |
| Mozilla | Firefox ESR | < 78.5 | — |
| Mozilla | Thunderbird | < 78.5 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | firefox-esr | 78.5.0esr-1 | — |
| Debian 14 | thunderbird | 1:78.5.0-1 | — |
| Debian 13 | firefox-esr | 78.5.0esr-1 | — |
| Debian 13 | thunderbird | 1:78.5.0-1 | — |
| Debian 12 | firefox-esr | 78.5.0esr-1 | — |
| Debian 12 | thunderbird | 1:78.5.0-1 | — |
| Debian 10 | firefox-esr | 78.5.0esr-1~deb10u1 | DSA-4793-1 |
| Debian 10 | thunderbird | 1:78.5.0-1~deb10u1 | DSA-4796-1 |
| Debian 9 | firefox-esr | 78.5.0esr-1~deb9u1 | DLA-2457-1 |
| Debian 9 | thunderbird | 1:78.5.0-1~deb9u1 | DLA-2464-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | firefox | 83.0+build2-0ubuntu0.20.04.1 | USN-4637-1 |
| Ubuntu 20.04 LTS | mozjs52 +1 | No fix yet | — |
| Ubuntu 20.04 LTS | thunderbird | 1:78.7.1+build1-0ubuntu0.20.04.1 | — |
| Ubuntu 18.04 LTS | firefox | 83.0+build2-0ubuntu0.18.04.2 | USN-4637-1 |
| Ubuntu 18.04 LTS | mozjs38 +1 | No fix yet | — |
| Ubuntu 18.04 LTS | thunderbird | 1:78.8.1+build1-0ubuntu0.18.04.1 | — |
| Ubuntu 16.04 LTS | firefox | 83.0+build2-0ubuntu0.16.04.3 | USN-4637-2 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8 | firefox +1 | 78.5.0-1.el8_3 | RHSA-2020:5237, RHSA-2020:5236 |
| RHEL 7 | firefox +1 | 78.5.0-1.el7_9 | RHSA-2020:5239, RHSA-2020:5235 |
| RHEL 6 | firefox +1 | 78.5.0-1.el6_10 | RHSA-2020:5257, RHSA-2020:5238 |
Show 3 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8.2 EUS | firefox +1 | 78.5.0-1.el8_2 | RHSA-2020:5234, RHSA-2020:5232 |
| RHEL 8.1 EUS | firefox +1 | 78.5.0-1.el8_1 | RHSA-2020:5233, RHSA-2020:5231 |
| RHEL 8.0 E4S | firefox +1 | 78.5.0-1.el8_0 | RHSA-2020:5314, RHSA-2020:5240 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP2 | MozillaFirefox | 78.5.0-8.17.1 | SUSE-SU-2020:3458-1 |
| SLES 15 SP2 | MozillaThunderbird | 78.5.0-3.107.1 | SUSE-SU-2020:3528-1 |
| SLES 15 SP1 | MozillaFirefox | 78.5.0-3.119.1 | SUSE-SU-2020:3383-1 |
| SLES 15 SP1 | MozillaThunderbird | 78.5.0-3.107.1 | SUSE-SU-2020:3528-1 |
| SLES 12 SP5 | MozillaFirefox | 78.5.0-112.36.1 | SUSE-SU-2020:3548-1 |
| SLES 12 SP4 | MozillaFirefox | 78.5.0-112.36.1 | SUSE-SU-2020:3548-1 |
| SLES 12 SP3 | MozillaFirefox | 78.5.0-112.36.1 | SUSE-SU-2020:3548-1 |
Show 13 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 12 SP2 | MozillaFirefox | 78.5.0-112.36.1 | SUSE-SU-2020:3548-1 |
| SLES 11 SP4 | MozillaFirefox | 78.5.0-78.105.1 | SUSE-SU-2020:14548-1 |
| SLES for SAP 12 SP5 | MozillaFirefox | 78.5.0-112.36.1 | SUSE-SU-2020:3548-1 |
| SLES for SAP 12 SP4 | MozillaFirefox | 78.5.0-112.36.1 | SUSE-SU-2020:3548-1 |
| SLES for SAP 12 SP3 | MozillaFirefox | 78.5.0-112.36.1 | SUSE-SU-2020:3548-1 |
| SLES for SAP 12 SP2 | MozillaFirefox | 78.5.0-112.36.1 | SUSE-SU-2020:3548-1 |
| SUSE OpenStack Cloud Crowbar 9 | MozillaFirefox | 78.5.0-112.36.1 | SUSE-SU-2020:3548-1 |
| SUSE OpenStack Cloud Crowbar 8 | MozillaFirefox | 78.5.0-112.36.1 | SUSE-SU-2020:3548-1 |
| SUSE OpenStack Cloud 9 | MozillaFirefox | 78.5.0-112.36.1 | SUSE-SU-2020:3548-1 |
| SUSE OpenStack Cloud 8 | MozillaFirefox | 78.5.0-112.36.1 | SUSE-SU-2020:3548-1 |
| SUSE OpenStack Cloud 7 | MozillaFirefox | 78.5.0-112.36.1 | SUSE-SU-2020:3548-1 |
| SUSE HPE Helion OpenStack 8 | MozillaFirefox | 78.5.0-112.36.1 | SUSE-SU-2020:3548-1 |
| SUSE Enterprise Storage 5 | MozillaFirefox | 78.5.0-112.36.1 | SUSE-SU-2020:3548-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | MozillaFirefox | 92.0-1.2 | openSUSE-SU-2024:10600-1 |
| openSUSE Tumbleweed | MozillaThunderbird | 91.1.1-1.1 | openSUSE-SU-2024:10601-1 |
| openSUSE Tumbleweed | firefox-esr | 128.5.1-1.1 | openSUSE-SU-2024:14572-1 |
| openSUSE Leap 15.2 | MozillaFirefox | 78.5.0-lp152.2.30.1 | openSUSE-SU-2020:2315-1, openSUSE-SU-2020:2020-1 |
| openSUSE Leap 15.2 | MozillaThunderbird | 78.5.0-lp152.2.19.1 | openSUSE-SU-2020:2096-1 |
| openSUSE Leap 15.1 | MozillaFirefox | 78.5.0-lp151.2.79.1 | openSUSE-SU-2020:2031-1 |
| openSUSE Leap 15.1 | MozillaThunderbird | 78.5.0-lp151.2.59.1 | openSUSE-SU-2020:2187-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | librewolf | 83.0-r0 | — |
| Alpine v3.23 | firefox +1 | 83.0-r0 | — |
| Alpine v3.23 | firefox-esr | 78.5.0-r0 | — |
| Alpine v3.23 | thunderbird | 78.5.1-r0 | — |
| Alpine v3.22 | firefox +1 | 83.0-r0 | — |
| Alpine v3.22 | firefox-esr | 78.5.0-r0 | — |
| Alpine v3.22 | thunderbird | 78.5.1-r0 | — |
| Alpine v3.21 | firefox +1 | 83.0-r0 | — |
| Alpine v3.21 | firefox-esr | 78.5.0-r0 | — |
| Alpine v3.21 | thunderbird | 78.5.1-r0 | — |
| Alpine v3.20 | firefox | 83.0-r0 | — |
| Alpine v3.20 | firefox-esr | 78.5.0-r0 | — |
| Alpine v3.20 | thunderbird | 78.5.1-r0 | — |
Show 8 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.19 | firefox | 83.0-r0 | — |
| Alpine v3.19 | firefox-esr | 78.5.0-r0 | — |
| Alpine v3.19 | thunderbird | 78.5.1-r0 | — |
| Alpine v3.18 | firefox | 83.0-r0 | — |
| Alpine v3.18 | firefox-esr | 78.5.0-r0 | — |
| Alpine v3.18 | thunderbird | 78.5.1-r0 | — |
| Alpine v3.17 | firefox | 83.0-r0 | — |
| Alpine v3.17 | firefox-esr | 78.5.0-r0 | — |
| Alpine v3.17 | thunderbird | 78.5.1-r0 | — |
| Alpine v3.16 | firefox | 83.0-r0 | — |
| Alpine v3.16 | firefox-esr | 78.5.0-r0 | — |
| Alpine v3.16 | thunderbird | 78.5.1-r0 | — |
| Alpine v3.15 | firefox | 83.0-r0 | — |
| Alpine v3.15 | firefox-esr | 78.5.0-r0 | — |
| Alpine v3.14 | firefox | 83.0-r0 | — |
| Alpine v3.14 | firefox-esr | 78.5.0-r0 | — |
| Alpine v3.13 | firefox | 83.0-r0 | — |
| Alpine v3.13 | firefox-esr | 78.5.0-r0 | — |
| Alpine v3.12 | firefox | 83.0-r0 | — |
| Alpine v3.12 | firefox-esr | 78.5.0-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2 | thunderbird | 78.6.0-1.amzn2 | ALAS2-2021-1586 |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 8 | firefox +1 | 78.5.0-1.0.1.el8_3 | ELSA-2020-5237, ELSA-2020-5236 |
| Oracle Linux 7 | firefox +1 | 78.5.0-1.0.1.el7_9 | ELSA-2020-5239, ELSA-2020-5235 |
Advisories 37
- RHSA-2020:5257 Red Hat Security Advisory: firefox security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- RHSA-2020:5239 Red Hat Security Advisory: firefox security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- RHSA-2020:5238 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- RHSA-2020:5235 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- USN-4637-2 firefox vulnerabilities Ubuntu Security Notices (USN) · Apr 22, 2026
- USN-4637-1 firefox vulnerabilities Ubuntu Security Notices (USN) · Apr 22, 2026
- DSA-4796-1 thunderbird - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DSA-4793-1 firefox-esr - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-2457-1 firefox-esr - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-2464-1 thunderbird - security update Debian Security (DSA / DLA) · Mar 9, 2026
- WID-SEC-2026-0337 Mozilla Firefox und Thunderbird: Mehrere Schwachstellen BSI CERT-Bund (WID) · Feb 8, 2026
- openSUSE-SU-2020:2096-1 Security update for MozillaThunderbird SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2020:14548-1 Security update for MozillaFirefox SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2020:2315-1 Security update for MozillaFirefox SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2020:3528-1 Security update for MozillaThunderbird SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2024:10600-1 MozillaFirefox-92.0-1.2 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2020:2031-1 Security update for MozillaFirefox SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2020:2020-1 Security update for MozillaFirefox SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2020:3458-1 Security update for MozillaFirefox SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2020:2187-1 Security update for MozillaThunderbird SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2020:3548-1 Security update for MozillaFirefox SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2024:14572-1 firefox-esr-128.5.1-1.1 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- RHSA-2020:5314 Red Hat Security Advisory: firefox security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2020:5240 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2020:5237 Red Hat Security Advisory: firefox security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2020:5236 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2020:5234 Red Hat Security Advisory: firefox security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2020:5233 Red Hat Security Advisory: firefox security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2020:5232 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- RHSA-2020:5231 Red Hat Security Advisory: thunderbird security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- openSUSE-SU-2024:10601-1 MozillaThunderbird-91.1.1-1.1 on GA media SUSE / openSUSE Security Updates · May 7, 2025
- SUSE-SU-2020:3383-1 Security update for MozillaFirefox SUSE / openSUSE Security Updates · May 2, 2025
- ALAS2-2021-1586 Important: thunderbird security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Jan 6, 2021
- ELSA-2020-5237 Important: firefox security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Dec 1, 2020
- ELSA-2020-5236 Important: thunderbird security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Dec 1, 2020
- ELSA-2020-5239 Important: firefox security update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Dec 1, 2020
- ELSA-2020-5235 Important: thunderbird security update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Dec 1, 2020