XSS in Mailerlite – Signup Forms (Official)

CVE-2025-13993

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.

Vulnerability class: XSS (Cross-Site Scripting)

Published · last modified .

CVSS v3 metric

CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.003 (25.3th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 25th percentile — 25.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2025-13993: held from 0.003 to 0.003.

EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: +0.000

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2025-13993?
CVE-2025-13993 is a medium-severity vulnerability in Mailerlite – Signup Forms (Official), classified under Cross-site Scripting. CVSS score: 5.5/10. Published 2025-12-12.
How severe is CVE-2025-13993?
Medium severity. CVSS v3 base score is 5.5 out of 10.