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
github.com/PrestaShop/ps_emailsubscription/commit/664ffb225e2afb4a32640bbedad667dc6e660b70
github.com/PrestaShop/ps_emailsubscription/releases/tag/v2.6.1
github.com/PrestaShop/ps_emailsubscription/security/advisories/GHSA-vwfx-hh3w-fj99
nvd.nist.gov/vuln/detail/CVE-2021-21418
packagist.org/packages/prestashop/ps_emailsubscription