XSS in Master Blocks

CVE-2026-88824

The Master Blocks WordPress plugin before 1.5.0 does not have authorisation on one of its REST routes, allowing unauthenticated users to update its settings, including a value that is output unescaped in the admin area, leading to Stored XSS that executes in the session of any administrator visiting a wp-admin page.

Vulnerability class: XSS (Cross-Site Scripting)

Published · last modified .

CVSS v3 metric

CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.005 (43.2th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 43rd percentile — 43.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-88824: held from 0.005 to 0.005.

EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000

Affected products

  • Master Blocks

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-88824?
CVE-2026-88824 is a high-severity vulnerability in Master Blocks, classified under Cross-site Scripting. CVSS score: 8.8/10. Published 2026-09-19.
How severe is CVE-2026-88824?
High severity. CVSS v3 base score is 8.8 out of 10.