CVE-2020-6823Public exploit

Account access via unchecked OAuth redirect URI

Published Apr 24, 2020 · Updated Aug 4, 2024

Missing authorization in Mozilla Firefox before 75 allows attackers to access service-provider accounts through a malicious extension. The browser.identity.launchWebAuthFlow API resolves its Promise with a redirect URL containing an authorization code even when the supplied redirect URI is not owned by the calling extension. Exploitation requires a malicious extension, a known registered OAuth redirect URI, and successful user authentication; the exposed code grants access to the account at that service provider.

CVSS severity9.8
Critical
EPSS probability1.61%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Missing authorization in Mozilla Firefox before 75 allows attackers to access service-provider accounts through a malicious extension. The browser.identity.launchWebAuthFlow API resolves its Promise with a redirect URL containing an authorization code even when the supplied redirect URI is not owned by the calling extension. Exploitation requires a malicious extension, a known registered OAuth redirect URI, and successful user authentication; the exposed code grants access to the account at that service provider.

The record

CVE
CVE-2020-6823
Published
Apr 24, 2020
Updated
Aug 4, 2024
Vendor
Mozilla
Product
Firefox
Classifications
CWE-862, T1528
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 24, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <75

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <75

Published CVSS scores

7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-862Missing Authorization
T1528Steal Application Access Token

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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