CVE-2026-0561

Shield Security <= 21.0.8 - Unauthenticated Reflected Cross-Site Scripting via 'message' Parameter

2026-02-18 16:17

Strategic Overview

Status: Patched in 21.0.10
Affected Plugin: Shield Security – Smart Bot Blocking, Brute-Force Login Protection & File Scanning
Affected Version: <= 21.0.8
CVSS: 6.1Medium
Weakness type: CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CVE: CVE-2026-0561

View all Shield Security – Smart Bot Blocking, Brute-Force Login Protection & File Scanning vulnerabilities

At a glance

CVE-2026-0561 is a medium-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the Shield Security WordPress plugin, affecting versions <= 21.0.8. It carries a CVSS score of 6.1 (reachable over the network; low attack complexity). Exploitation requires no authentication. The issue is fixed in version 21.0.10; sites on affected versions should update now. Disclosed February 2026, reported by Dmitrii Ignatyev.

Vulnerability Overview

The Shield Security plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the 'message' parameter in all versions up to, and including, 21.0.8 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a link.

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 privileges on the target site.

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

Shield Security <= 21.0.8 carries this weakness at message, and reaching it takes no account at all. 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 Shield Security the fix is 21.0.10: builds <= 21.0.8 are affected, anything from 21.0.10 onward is not.

Remediation

Update to version 21.0.10, or a newer patched version

How does WordSec protect against this?

Requests carrying this pattern arrive without a session, so nothing upstream of the firewall gets a chance to reject them: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: Shield Security 21.0.10 closes this, and updating the plugin is the step that ends it.

Firewall
Login Security
Alerts

External References

https://www.cve.org/CVERecord?id=CVE-2026-0561 https://www.wordfence.com/threat-intel/vulnerabilities/id/cb49eb5f-c1ff-4440-8b53-c2515e65da27 https://nvd.nist.gov/vuln/detail/CVE-2026-0561

Related records

Same weakness class

Other vulnerabilities in Shield Security – Smart Bot Blocking, Brute-Force Login Protection & File Scanning

CVSS Vector

6.1

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Base

Attack VectorNetwork
Attack ComplexityLow
Privileges RequiredNone
User InteractionRequired
ScopeChanged
ConfidentialityLow
IntegrityLow
AvailabilityNone

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