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MasterStudy LMS CVE-2026-81340

| EUVDEUVD-2026-82658 LOW
Authorization Bypass Through User-Controlled Key (CWE-639)
2026-09-18 WPScan GHSA-332v-j356-q3mj
3.8
CVSS 3.1 · Vendor: WPScan
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Attack ChainAIDerived

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

  1. Access
    Obtain Instructor-role account
  2. Exploit
    Enumerate arbitrary order IDs
  3. Execution
    Call order-update REST endpoint without ownership check
  4. Impact
    Grant free enrolment / revoke paid enrolments / tamper notes

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V8 - Authorization Object-level authorization, IDOR prevention
Exploitation Conditions

Requires an authenticated account holding the WordPress 'Instructor' role on a site running MasterStudy LMS plugin before 3.7.50; no administrator privileges and no victim user interaction are needed. The flaw is reachable via the plugin's order-management REST API, which fails to perform per-object ownership or capability checks. Limiting factor: the attacker must already possess (or be granted/self-register into) the Instructor role, which is the primary constraint on real-world exploitation; default configurations of the plugin are affected once such an account exists.

Impact

This is a genuine but moderate-severity broken-authorization (IDOR) flaw. Signals: CVSS:3.1 vector is AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:L (vendor score 3.8). A public POC exists (WPScan), a patch is available (3.7.50), but there is NO EPSS score and NO CISA KEV listing provided - status is 'publicly available exploit code exists', not active exploitation. The key CONFLICT: the vendor sets PR:H, yet the description states exploitation only requires the Instructor role, which is a mid-tier registered WordPress role, not an administrator. Instructor should be PR:L, not PR:H - correcting this raises the base score to roughly 5.4. Impact is correctly limited to integrity/availability (grant free enrolments, revoke others' paid enrolments, tamper order notes) with no confidentiality read (C:N). Net: a real but bounded priority - it requires an attacker to already hold an Instructor account, which caps mass exploitability, so treat it as a moderate patch-soon issue rather than an emergency.

Exploit ScenarioDerived

An attacker who registers or is granted an Instructor account on a MasterStudy LMS site sends crafted requests to the order-update REST API endpoint referencing order IDs they do not own. Because no per-object ownership or capability check is enforced, they grant themselves free enrolment in paid courses, revoke other students' paid enrolments, and rewrite order notes. A public POC is available via WPScan, lowering the skill needed.

Monitor Track and reassess. Why: LOW severity (CVSS 0.1-3.9).
Patch available 0.1% exploitation probability (EPSS)

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AnalysisAIv1 – Sep 18, 2026

Broken object-level authorization in the MasterStudy LMS WordPress plugin before 3.7.50 lets an authenticated user holding the Instructor role modify any order on the site through the plugin's order REST API, enabling free course enrolment, revocation of other users' paid enrolments, and tampering with order notes. The flaw is an IDOR (CWE-639) reachable remotely over the network with low privileges required and no victim interaction; publicly available exploit code exists, though there is no confirmation of active exploitation (CISA KEV). Our assessed vector (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L) places this at moderate severity, with the Instructor account requirement being the principal real-world constraint.

RemediationAI

Vendor-released patch: upgrade MasterStudy LMS to 3.7.50 or later - this is the only complete fix, since the underlying defect is missing server-side ownership/capability validation in the plugin's order REST handlers. Per the vendor advisory (https://wpscan.com/vulnerability/8006876f-27bb-483d-b4e4-9fa4414d16f0/), the patched release corrects the absent per-object permission checks. Where immediate upgrade is not possible, apply these compensating controls with awareness of their trade-offs: (1) audit and prune Instructor-role accounts, temporarily downgrading them to Student or Subscriber - this preserves the role boundary but degrades legitimate instructor workflows and does not fix the API for any retained Instructor; (2) if the site allows users to self-select or self-register into the Instructor role, disable that path in the plugin/WordPress registration settings immediately, as it is the easiest route to satisfying the attacker prerequisite; (3) block or rate-limit unauthenticated and low-privilege access to the plugin's order REST routes at the WAF/reverse-proxy layer (filtering on the plugin's REST namespace and order endpoints) - this is a blunt control that will break legitimate front-end order operations and must be tested before enforcement; (4) add a short-term mu-plugin filter enforcing current_user_can and order-ownership checks on the order-update route, accepting that custom code must be maintained and re-validated against the vendor patch; (5) monitor order records for unexpected enrolment grants, revoked paid enrolments, or modified order notes, since those are the observable artifacts of exploitation. Note that restricting REST access without upgrading leaves the code-level IDOR in place for any reachable path.

Affected VersionsENISA

MasterStudy LMS WordPress Plugin 0 <3.7.50

Affected Packages

euvd masterstudy_lms_wordpress_plugin fix: 3.7.50

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 affected component is the MasterStudy LMS WordPress plugin, a course-and-commerce extension that manages courses, students, instructors, and paid enrolments through orders processed via its own REST API namespace. The root cause is CWE-639, Authorization Bypass Through User-Controlled Key: order-update handlers accept an order identifier supplied by the client but fail to verify that the requesting user owns that object or holds a capability permitting modification of it. WordPress capability checks (current_user_can) and object-ownership comparisons against order metadata are therefore missing, so authorization degenerates into authentication only. Because the plugin's orders are tightly coupled to enrolment state and payment status, an attacker who can write to arbitrary order records can indirectly grant or revoke course access and alter financial/administrative notes. Note that the CPE data maps the product to an 'unknown' vendor entry (cpe:2.3:a:unknown:masterstudy_lms_wordpress_plugin:*:*:*:*:*:*:*:*), a normalization gap rather than a distinct affected product; the plugin is distributed through the WordPress ecosystem and its stated maintainer, not a CPE-listed vendor.

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Severity by source

Vendor (WPScan) PRIMARY 3.8 LOW
AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:L
vuln.today AI 5.4 MEDIUM

Instructor is a mid-tier authenticated role so PR:L (not vendor PR:H); order tampering/free enrolment is I:L and revoking paid enrolments is A:L; no data read so C:N.

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

Primary rating from Vendor (WPScan).

CVSS VectorVendor: WPScan

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

Lifecycle Timeline

3
Patch available
Sep 18, 2026 - 07:01 EUVD
CVE Published
Sep 18, 2026 - 06:00 cve.org
UNKNOWN (no severity yet)
CVE Published
Sep 18, 2026 - 06:00 cve.org
LOW 3.8

DescriptionCVE.org

The MasterStudy LMS WordPress Plugin WordPress plugin before 3.7.50 does not perform per-object ownership or capability checks when updating orders through its REST API, allowing users with the Instructor role to modify any order on the site, granting free course enrolment, revoking other users' paid enrolments, and tampering with order notes.

Threat Intelligence Overview

EPSS Score
0.1%
Top 96% exploitable
Prevalence
Medium
popular WordPress LMS plugin, roughly 100k+ active installs
Exploit
POC
Public exploit code exists
Data Quality
4 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 LOW
CISA KEV No
Public POC Yes
EPSS 0.1%
Patch available Yes
Active threat No
Deciding rule
LOW severity (CVSS 0.1-3.9)
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
No
Human Impact· derived
Low
Technical Impact
Partial

Priority Score

39
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +19
PoC: +20
Weaponized: 0
Threat intel: 0
Gov advisory: 0
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