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Vulnerability details: VCID-fqfv-4vrw-4uau
Vulnerability ID VCID-fqfv-4vrw-4uau
Aliases CVE-2021-23984
Summary A malicious extension could have opened a popup window lacking an address bar. The title of the popup lacking an address bar should not be fully controllable, but in this situation was. This could have been used to spoof a website and attempt to trick the user into providing credentials.
Status Published
Exploitability None
Weighted Severity None
Risk None
Affected and Fixed Packages Package Details
Weaknesses (1)
CWE-1021 Improper Restriction of Rendered UI Layers or Frames
System Score Found at
cvssv3 6.1 https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-23984.json
epss 0.0029 https://api.first.org/data/v1/epss?cve=CVE-2021-23984
cvssv3.1 6.1 https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
archlinux High https://security.archlinux.org/AVG-1728
archlinux High https://security.archlinux.org/AVG-1729
generic_textual high https://www.mozilla.org/en-US/security/advisories/mfsa2021-10
generic_textual high https://www.mozilla.org/en-US/security/advisories/mfsa2021-11
generic_textual high https://www.mozilla.org/en-US/security/advisories/mfsa2021-12
Reference id Reference type URL
https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-23984.json
https://api.first.org/data/v1/epss?cve=CVE-2021-23984
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-23981
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-23982
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-23984
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-23987
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29950
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29955
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-4127
https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
1942786 https://bugzilla.redhat.com/show_bug.cgi?id=1942786
AVG-1728 https://security.archlinux.org/AVG-1728
AVG-1729 https://security.archlinux.org/AVG-1729
GLSA-202104-09 https://security.gentoo.org/glsa/202104-09
GLSA-202104-10 https://security.gentoo.org/glsa/202104-10
mfsa2021-10 https://www.mozilla.org/en-US/security/advisories/mfsa2021-10
mfsa2021-11 https://www.mozilla.org/en-US/security/advisories/mfsa2021-11
mfsa2021-12 https://www.mozilla.org/en-US/security/advisories/mfsa2021-12
RHSA-2021:0989 https://access.redhat.com/errata/RHSA-2021:0989
RHSA-2021:0990 https://access.redhat.com/errata/RHSA-2021:0990
RHSA-2021:0991 https://access.redhat.com/errata/RHSA-2021:0991
RHSA-2021:0992 https://access.redhat.com/errata/RHSA-2021:0992
RHSA-2021:0993 https://access.redhat.com/errata/RHSA-2021:0993
RHSA-2021:0994 https://access.redhat.com/errata/RHSA-2021:0994
RHSA-2021:0995 https://access.redhat.com/errata/RHSA-2021:0995
RHSA-2021:0996 https://access.redhat.com/errata/RHSA-2021:0996
USN-4893-1 https://usn.ubuntu.com/4893-1/
USN-4995-1 https://usn.ubuntu.com/4995-1/
USN-4995-2 https://usn.ubuntu.com/4995-2/
No exploits are available.
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-23984.json
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Exploit Prediction Scoring System (EPSS)
Percentile 0.52642
EPSS Score 0.0029
Published At May 29, 2026, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2026-05-29T08:26:32.057089+00:00 Mozilla Importer Import https://github.com/mozilla/foundation-security-advisories/blob/master/announce/2021/mfsa2021-10.yml 38.6.0