CVE-2026-90981

Newsletter <= 9.3.8 - Reflected Cross-Site Scripting via 'nn' Parameter

2026-09-17 18:40
Yuto Hyakumoto

Strategic Overview

Status
Patched in 9.3.9
Affected Plugin
Newsletter – Send awesome emails from WordPress
Affected Version
<= 9.3.8
CVSS
6.1Medium
Weakness type
CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CVE
CVE-2026-90981
View all Newsletter – Send awesome emails from WordPress vulnerabilities

At a glance

CVE-2026-90981 is a medium-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the Newsletter WordPress plugin, affecting versions <= 9.3.8. 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 9.3.9; sites on affected versions should update now. Disclosed September 2026, reported by Yuto Hyakumoto.

Vulnerability Overview

The Newsletter – Send awesome emails from WordPress plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the 'nn' parameter in all versions up to, and including, 9.3.8 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. Successful exploitation requires the victim to be a logged-in administrator, as the antibot check auto-passes for authenticated users, routing the unsanitized payload through the administrator-visible output branch of dienow().

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')

Newsletter <= 9.3.8 carries this weakness at dienow(), and reaching it takes a caller who can reach the endpoint. 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 Newsletter the fix is 9.3.9: builds <= 9.3.8 are affected, anything from 9.3.9 onward is not.

Remediation

Update to version 9.3.9, or a newer patched version

How does WordSec protect against this?

The attempt arrives as an ordinary request to Newsletter: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: Newsletter 9.3.9 closes this, and updating the plugin is the step that ends it.

  • Firewall
  • Alerts

External References

https://www.cve.org/CVERecord?id=CVE-2026-90981https://www.wordfence.com/threat-intel/vulnerabilities/id/44b3b015-2482-4b80-b208-73f1abe21b27https://nvd.nist.gov/vuln/detail/CVE-2026-90981

Related records

Vulnerability data © Defiant, Inc., provided under the Wordfence Intelligence T&C