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CVE-2026-27543 – Unauthenticated Privilege Escalation – MStore API WordPress Plugin (≤ 4.20.0)

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Summary

CVE-2026-27543 is an unauthenticated privilege escalation vulnerability affecting the MStore API WordPress plugin (developed by FluxBuilder), versions up to and including 4.20.0. The flaw stems from incorrect privilege assignment (CWE-266) and allows an attacker with no authentication to escalate privileges on affected WordPress sites. It carries a CVSS v3.1 base score of 8.1 (High).

Technical details

  • Root cause: Incorrect privilege assignment (CWE-266) within the MStore API plugin’s account/role-handling logic.
  • Trigger conditions: No authentication or user interaction is required to trigger the flaw, though the attack complexity is rated High.
  • Attack vector: Network — exploitable remotely against any internet-exposed WordPress site running the vulnerable plugin.
  • Impact: Successful exploitation allows an unauthenticated attacker to escalate privileges, with full impact on confidentiality, integrity, and availability of the affected site.

Affected software

  • MStore API (WordPress plugin) versions ≤ 4.20.0
  • Fixed in version 4.21.0

Severity

  • CVSS v3.1 Base Score: 8.1 (High)
  • Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Mitigation and recommended actions

  • Immediate: Update the MStore API WordPress plugin to version 4.21.0 or later, where the privilege escalation flaw is fixed.
  • If immediate patching is not possible: Restrict or monitor access to the WordPress site’s REST API and admin-facing endpoints, and review user accounts for unauthorized role changes or newly created accounts with elevated privileges.

How IONIX identifies potentially affected assets

IONIX matches the following signals against data already collected when it crawled the asset; identifying the technology sends no request beyond that crawl.

  • Raw HTTP response body: /wp-content/plugins/mstore-api/

References

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How IONIX’s External Exposure Management Platform Detects and Validates
Zero-Days to Shrink MTTR

1

Map your entire attack surface (continously)

IONIX uses multi-factor discovery methods, including DNS analysis, certificate mapping, metadata inspection, and more, to automatically map every internet-facing asset across your environment. This includes cloud instances, third-party platforms, shadow IT, and even forgotten infrastructure that traditional tools miss.

2

Monitor for new CVEs

Dozens of threat intel feeds using agentic technology are continuously analyzed to detect the appearance of proof-of-concept code, exploit kits, and indicators of active targeting. IONIX goes further by applying AI to proactively evaluate whether emerging vulnerabilities are likely to be exploited, even before PoCs go public.

3

Identify Potential External Exposures

Not all CVEs matter. IONIX filters vulnerabilities by asking attacker-centric questions: Can it be reached from the internet? Does it require authentication? Is it being exploited in the wild? This dramatically reduces noise and focuses teams on threats that can actually be weaponized.

4

Create Safe, Scalable Exploit Validations

IONIX transforms real-world PoCs into safe, non-intrusive test payloads that can be run in production environments without disruption. These simulations are precisely targeted to the systems that are vulnerable, ensuring rapid validation without unnecessary load.

5

Execute Exploit Validations

By combining context about software stack, versioning, exposure status, and reachability, IONIX ensures that only the right payloads are executed against the right assets, maximizing efficiency and minimizing risk.

6

Drive Fast and Actionable Remediation

Results are routed through integrations with ticketing, SOAR, and SIEM tools. Issues are written in plain language, bundled into remediation clusters, and prioritized based on asset criticality, exploitability, and blast radius. This shortens mean time to remediation (MTTR) and empowers teams to act with confidence.

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  • Mapping of all Assets with this Technology
  • Identification of potentially exposed assets to this CVE
  • Confirmation of verified exploitable assets
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