CVE-2026-12900

Spectra Gutenberg Blocks <= 2.19.28 - Authenticated (Contributor+) Stored Cross-Site Scripting via uagb/image Block

2026-07-20 09:16
theviper17y

Strategic Overview

Status
Patched in 2.19.29
Affected Plugin
Spectra Legacy – Gutenberg Blocks
Affected Version
<= 2.19.28
CVSS
6.4Medium
Weakness type
CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CVE
CVE-2026-12900
View all Spectra Legacy – Gutenberg Blocks vulnerabilities

At a glance

CVE-2026-12900 is a medium-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the Spectra Legacy WordPress plugin, affecting versions <= 2.19.28. It carries a CVSS score of 6.4 (reachable over the network; low attack complexity). Exploitation requires an authenticated account at Contributor level or above. The issue is fixed in version 2.19.29; sites on affected versions should update now. Disclosed July 2026, reported by theviper17y.

Vulnerability Overview

The Spectra Gutenberg Blocks – Website Builder for the Block Editor plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the `uagb/image` block in all versions up to, and including, 2.19.28 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with Contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.

Technical Analysis

The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no interaction from a victim user.

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Reaching this weakness in Spectra Legacy <= 2.19.28 takes an account at Contributor level or above. Cross-site scripting happens when input from a request is written into a page without being escaped for the context it lands in, so the browser parses attacker-supplied text as markup or script.

Injected script runs with the privileges of whoever views the affected page, which is how these flaws turn into administrator session theft, silent account creation or persistent backdoors in page content. For Spectra Legacy the fix is 2.19.29: builds <= 2.19.28 are affected, anything from 2.19.29 onward is not.

Remediation

Update to version 2.19.29, or a newer patched version

How does WordSec protect against this?

An attacker needs Contributor access first, so the firewall sees the attempt as traffic from a logged-in account: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: Spectra Legacy 2.19.29 closes this, and updating the plugin is the step that ends it.

  • Firewall
  • Alerts

External References

https://www.cve.org/CVERecord?id=CVE-2026-12900https://www.wordfence.com/threat-intel/vulnerabilities/id/0e9dc5e3-9d72-4c04-8ba9-56428a6fddddhttps://nvd.nist.gov/vuln/detail/CVE-2026-12900

Related records

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