CVE-2023-23603Public exploitNetwork attack vector

Data exfiltration via console style URL bypass

Published Jun 2, 2023 · Updated Dec 18, 2025

CSP bypass in Mozilla Firefox before 109, Firefox ESR before 102.7, and Thunderbird before 102.7 allows remote attackers to exfiltrate data. The DevTools cleanupStyle filter uses a forbidden-pattern regular expression that accepts obfuscated external URLs in console.log %c styles. A victim must open Developer Tools on attacker-controlled content; the resulting resource request can transmit browser-accessible data.

CVSS severity6.5
Medium
EPSS probability0.64%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

CSP bypass in Mozilla Firefox before 109, Firefox ESR before 102.7, and Thunderbird before 102.7 allows remote attackers to exfiltrate data. The DevTools cleanupStyle filter uses a forbidden-pattern regular expression that accepts obfuscated external URLs in console.log %c styles. A victim must open Developer Tools on attacker-controlled content; the resulting resource request can transmit browser-accessible data.

The record

CVE
CVE-2023-23603
Published
Jun 2, 2023
Updated
Dec 18, 2025
Vendor
Mozilla
Product
Firefox
Classifications
CWE-770
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 2, 2023CVE publishedPublication date reported by the CVE source.
  2. Dec 18, 2025Record 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 <109

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <109
Mozilla · Thunderbirdversion=unspecified <102.7
Mozilla · Firefox ESRversion=unspecified <102.7

Published CVSS scores

6.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling

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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