Security readout for executives and security teams
Plain-English summary
CVE-2026-0559 is a stored cross-site scripting issue in the MasterStudy LMS WordPress plugin. A logged-in user with Contributor-level access or higher could place malicious script content through a course grid shortcode. That script may run when others view the affected page, creating account, data, or site-trust risk.
Executive priority
Treat as a medium-priority web application issue. Prioritize sites with many content contributors, online course authors, or external instructors. Patch during the next security maintenance window, sooner for public, high-traffic, or revenue-generating learning sites.
Technical view
The flaw affects MasterStudy LMS WordPress Plugin – for Online Courses and Education versions up to and including 3.7.11. It is caused by insufficient sanitization and output escaping of user-supplied attributes in the stm_lms_courses_grid_display shortcode. CVSS 3.1 is 6.4, CWE-79, with low privileges required and changed scope.
Likely exposure
Exposure is most relevant for WordPress sites running MasterStudy LMS at version 3.7.11 or earlier, especially where Contributors, Authors, instructors, or other semi-trusted users can create pages or posts containing shortcodes.
Exploitation context
The source bundle does not show CISA KEV listing or other evidence of active exploitation. Exploitation requires authenticated Contributor-or-higher access, but no user interaction is required once an injected page is viewed.
Researcher notes
The evidence identifies a stored XSS in shortcode attribute handling, not a remote unauthenticated takeover. The provided references include a Wordfence advisory and a WordPress plugin Trac changeset, but the bundle does not include exploit evidence or detailed vendor remediation text.
Mitigation direction
- Identify all WordPress sites using MasterStudy LMS.
- Upgrade MasterStudy LMS beyond 3.7.11 if a vendor-fixed version is available.
- Review the vendor changelog and WordPress plugin repository guidance.
- Restrict Contributor-or-higher access to trusted users only.
- Review pages and posts using the affected shortcode for suspicious attributes.
Validation and detection
- Confirm installed MasterStudy LMS version on each WordPress site.
- Check whether the plugin version is 3.7.11 or earlier.
- Inventory users with Contributor-level access or higher.
- Search content for stm_lms_courses_grid_display shortcode usage.
- Verify updated plugin behavior escapes shortcode attributes safely in staging.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-79: User-session and phishing behavior lookup
Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-0559 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 6.4 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N3.12.7Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.4MediumVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.