CVE-2021-23986

MEDIUM
6.5
CVSS Score
Published: March 31, 2021 at 01:41 PM UTC
Updated: June 17, 2026 at 03:39 AM UTC
1 product affected across 1 vendorFirefox

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Severity
MEDIUM6.5
Exploit prediction
EPSS 0.4%

Description

A malicious extension with the 'search' permission could have installed a new search engine whose favicon referenced a cross-origin URL. The response to this cross-origin request could have been read by the extension, allowing a same-origin policy bypass by the extension, which should not have cross-origin permissions. This cross-origin request was made without cookies, so the sensitive information disclosed by the violation was limited to local-network resources or resources that perform IP-based authentication. This vulnerability affects Firefox < 87.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 87
Affected range stops below 87, so it looks safe — our inference, not a vendor statement
Affected range stops below 87.0, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

References (2)

x_refsource_MISCIssue TrackingPermissions RequiredVendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1692623

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
NONE
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-346

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