External risk intelligence

Newsletter Subscription Form SQL Injection

CVE advisorySeverity: CRITICAL (CVSS 9.3)

CVE-2026-41555

The vulnerability exists in a newsletter subscription form within a web plugin. Such forms are designed to be public-facing and accessible to internet users to capture email addresses, making them inherently internet-exposed in normal, intended deployments.

SQL Injection

Halo Surface Signal: 5 out of 5 — more likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A critical vulnerability has been identified in a newsletter subscription form plugin, specifically in how it handles email capture. This flaw could potentially allow unauthorized access to backend data if exploited, impacting the confidentiality of information. The main concern at this stage is to confirm if this specific plugin and version are in use within our environment.

Flaw in email capture of a subscription form.
Unauthenticated data access could be a risk.
Confirm relevance and exposure to understand impact.

Attack Path

How an attacker could exploit the issue

An attacker could target a website's newsletter subscription form, which is accessible over the internet, to inject malicious SQL code. This could happen without any prior authentication or special privileges. By manipulating the email capture field, an attacker could potentially disrupt the website's database operations or gain unauthorized access to sensitive information.

No authentication required for access.
Triggered by submitting a crafted email address.
Risk of database compromise and disruption.

Live Threat

Current exploitation, exposure, and threat context

When supported by the advisory, unauthenticated SQL injection in a newsletter subscription form could allow an attacker to access or manipulate user subscription data. The vulnerability could also affect the integrity and availability of the service by disrupting its normal operation.

User subscription data.
Malicious SQL queries sent to the form.
Service disruption or data exposure.

Operational Fix

Recommended remediation, mitigation, and detection steps

This critical vulnerability in newsletter subscription forms likely falls under the purview of application owners and web platform teams, with input from security and network teams for exposure assessment. The immediate first step is to locate all instances of the affected plugin, confirm their reachability and business criticality, and identify the accountable owners to prioritize remediation efforts.

Application owners and platform teams.
Verify public-facing instances and business impact.
Plan coordinated remediation based on risk.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is the Newsletter Subscription Form plugin?

It is a WordPress plugin designed to add email subscription functionality to websites. Users typically install it to manage newsletter sign-ups, allowing visitors to enter their contact information directly into a form on the site to join a mailing list.

What does SQL injection mean for CVE-2026-41555?

This vulnerability is classified as CWE-89, meaning the software fails to properly sanitize user input before including it in database queries. Because the email field does not filter malicious commands, an attacker can manipulate the underlying database structure or read information they are not authorized to access.

How is this SQL injection triggered?

An attacker triggers the flaw by submitting a specially crafted email address through the plugin's subscription form. The vulnerability does not require the attacker to have an account or login privileges. Simply interacting with the public-facing subscription field is sufficient to execute the malicious input, provided the plugin version is 1.5.9 or older.

Is my website at risk from this vulnerability?

Halo Surface Signal indicates this vulnerability is highly likely to be internet-exposed because it resides in a subscription form designed for public access. If your website uses the affected plugin version and the form is reachable by anyone on the internet, your backend database is potentially accessible to unauthorized parties.

What should I do if I use this plugin?

Begin by identifying every instance of the Newsletter Subscription Form plugin running in your environment. Confirm which of these forms are reachable from the internet and coordinate with your web platform or application owners to assess the business impact and prioritize a remediation plan.

References

patchstack.com/database/wordpress/plugin/newsletter-subscription-for…

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.