What the vulnerability does
01Description
The MailerLite – Signup forms (official) plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'form_description' and 'success_message' parameters in versions up to, and including, 1.7.16 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with administrator access or higher, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
Explanation of Vulnerability in Simple Terms
02Summary
MailerLite Signup Forms versions 1.7.16 and earlier contain a cross-site scripting vulnerability that allows high-privilege users to inject malicious scripts. The vulnerability has a changed scope, meaning injected code can affect other users or components beyond the vulnerable form itself. Site administrators should update to a version newer than 1.7.16 to mitigate this risk.
What an attacker can do
03Attacker Capabilities
Inject malicious JavaScript that executes in other users' browsers when they interact with signup forms.
Potential impact on your site
04Site Impact
Compromised admin accounts could inject malicious code affecting all site visitors using signup forms.
Conditions required to exploit
05Prerequisites
Attacker must have high-level administrative privileges on the site; no user interaction required.
Key dates
06Disclosure timeline
December 12, 2025
CVE published
April 8, 2026
Record updated
