Client-side object modification via DataTables setter
Published Mar 16, 2026 · Updated Mar 16, 2026
Prototype pollution in RS Studio Lagom WHMCS Client Theme 2.3.0 through 2.3.7 allows attackers to alter browser object behavior. The bundled DataTables _fnSetObjectDataFn accepts a dot-delimited path containing proto and writes the supplied value onto Object.prototype without blocking prototype keys. The public proof of concept requires JavaScript to run in a visitor browser and demonstrates toString replacement and alert execution, so the established consequence is client-side integrity modification rather than server compromise.
Summary
What happened
Prototype pollution in RS Studio Lagom WHMCS Client Theme 2.3.0 through 2.3.7 allows attackers to alter browser object behavior. The bundled DataTables _fnSetObjectDataFn accepts a dot-delimited path containing proto and writes the supplied value onto Object.prototype without blocking prototype keys. The public proof of concept requires JavaScript to run in a visitor browser and demonstrates toString replacement and alert execution, so the established consequence is client-side integrity modification rather than server compromise.
The record
- CVE
- CVE-2026-4239
- Published
- Mar 16, 2026
- Updated
- Mar 16, 2026
- Vendor
- RS Studio
- Product
- Lagom WHMCS Client Theme
- Classifications
- CWE-94, CWE-1321, T1203
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Mar 16, 2026CVE publishedPublication date reported by the CVE source.
- Mar 16, 2026Record 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.
- Affected versionversion=2.3.0
- Affected versionversion=2.3.1
- Affected versionversion=2.3.2
- Affected versionversion=2.3.3
- Affected versionversion=2.3.4
- Affected versionversion=2.3.5
- Affected versionversion=2.3.6
- Affected versionversion=2.3.7
What conditions does exploitation require?
What is affected?
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.
Weakness, pattern, technique
Public exploit references
- Lagom WHMCS Template prototype-pollution proof of conceptproof of concept · demonstrated
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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