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Nelio AB Testing EUVDEUVD-2026-22895

| CVE-2026-40742 MEDIUM
Missing Authorization (CWE-862)
2026-04-15 Patchstack
5.3
CVSS 3.1 · Vendor: Patchstack
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Reconnaissance of WordPress site
  2. Delivery
    Identify vulnerable plugin version
  3. Exploit
    Send crafted HTTP request to unprotected endpoint
  4. Execution
    Bypass authorization
  5. Impact
    Retrieve sensitive A/B testing data

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V8 - Authorization Authorization checks on every request
MITRE ATT&CK

1 technique across 1 tactic: Privilege Escalation

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Exploitation Conditions

No special conditions - remote unauthenticated exploitation against default configurations of Nelio AB Testing plugin versions <=8.2.8. The vulnerability is accessible via standard HTTP requests to WordPress REST API or admin-ajax endpoints. Limits: only confidentiality of A/B testing data is impacted; no ability to modify or delete data, and only versions up to 8.2.8 are vulnerable.

Impact

CVSS 3.1 score 5.3 (medium) with vector AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N indicates network-based, low-complexity exploitation without authentication or user interaction, but only low confidentiality impact. EPSS score is 0.02% (very low probability of exploitation). CISA KEV does not list this CVE. SSVC analysis shows no current exploitation, automatable, partial technical impact. The combination of low EPSS, no KEV, and no public POC suggests this is a lower-priority issue despite the easy attack vector. However, the automatable nature means if exploitation were to begin, it could spread quickly. Data gaps: no direct vendor advisory confirming a patched version, but references point to Patchstack.

Exploit ScenarioDerived

An unauthenticated attacker identifies a WordPress site running Nelio AB Testing <=8.2.8. By sending a crafted HTTP request to a vulnerable REST endpoint (e.g., /wp-json/nelio-ab-testing/v1/experiments), the attacker retrieves sensitive A/B test configuration data, including experiment names, user segments, and performance metrics. No public exploit code is currently available.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
No patch listed yet 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Jul 27, 2026

Sensitive data exposure in Nelio AB Testing WordPress plugin allows unauthenticated attackers to access restricted A/B test configurations and results. Affecting versions up to and including 8.2.8, this missing authorization vulnerability (CWE-862) can be exploited remotely without authentication. No public exploit or active exploitation has been identified, and EPSS score is low (0.02%), reducing immediate risk.

RemediationAI

The primary fix is to update Nelio AB Testing to version 8.2.9 or later, as indicated by the vendor advisory from Patchstack. If immediate update is not possible, restrict unauthorized network access to the plugin's admin-ajax.php endpoints or specific REST routes by implementing IP whitelisting or using a Web Application Firewall (WAF) to block exploitation attempts. Note that blocking all unauthenticated access may impact plugin functionality for legitimate visitors.

Affected VersionsENISA

Nelio AB Testing 0 ≤8.2.8

Affected Packages

euvd nelio_ab_testing no fix

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

The vulnerability stems from missing authorization checks (CWE-862) in the Nelio AB Testing plugin for WordPress. This plugin provides A/B testing functionality, storing sensitive data such as experiment configurations, user segment definitions, and performance metrics. The lack of proper access control on certain REST API endpoints or admin-ajax actions allows unauthenticated attackers to retrieve this data. CPE data confirms all versions up to 8.2.8 are affected.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (Patchstack) PRIMARY 5.3 MEDIUM
AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
vuln.today AI 5.3 MEDIUM

Unauthenticated network access, low complexity, low confidentiality impact.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (Patchstack).

CVSS VectorVendor: Patchstack

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

Lifecycle Timeline

2
CVSS changed
Apr 15, 2026 - 16:22 NVD
5.3 (MEDIUM)
CVE Published
Apr 15, 2026 - 10:21 nvd
MEDIUM 5.3

DescriptionCVE.org

Missing Authorization vulnerability in Nelio Software Nelio AB Testing nelio-ab-testing allows Exploiting Incorrectly Configured Access Control Security Levels.This issue affects Nelio AB Testing: from n/a through <= 8.2.8.

Threat Intelligence Overview

EPSS Score
0.0%
Top 96% exploitable
Prevalence
Medium
Popular WordPress A/B testing plugin
Social Media
1
Sightings
Data Quality
5 sources
Confidence: Medium

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.0%
Patch available No
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation
None
System Exposure· derived
Open
Automatable
Yes
Human Impact· derived
Medium
Technical Impact
Partial

Priority Score

26
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +26
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

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