CVE-2021-21418 is a medium-severity (CVSS 5.4) Cross-site Scripting (XSS) vulnerability in prestashop/ps_emailsubscription. A fix is available for prestashop/ps_emailsubscription — see the affected versions and patch details below.
Potential XSS injection in the newsletter conditions field
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-21418 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
prestashop/ps_emailsubscriptionReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
ps_emailsubscription is a newsletter subscription module for the PrestaShop platform. An employee can inject javascript in the newsletter condition field that will then be executed on the front office The issue has been fixed in 2.6.1
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | prestashop/ps_emailsubscription | all versions | 2.6.1composer require prestashop/ps_emailsubscription:^2.6.1 |
Affected Products
ps emailsubscriptionprestashopDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for prestashop/ps_emailsubscription, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update prestashop/ps_emailsubscription to 2.6.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21418 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Frequently Asked Questions
Is CVE-2021-21418 in your dependencies?
Find it across Packagist, including transitive dependencies.