Ninja Forms plugin for WordPress versions 3.10.4 through 3.14.9 contains an unauthenticated stored cross-site scripting vulnerability in the Repeatable Fieldset feature where parseSubmissionIndex() accepts arbitrary strings as submission indexes without numeric validation, and admin_form_element() interpolates the index directly into HTML without escaping. An unauthenticated attacker can submit a public form with a crafted repeater child key containing malicious script payloads, which execute in an administrator's browser when viewing submissions in the WordPress admin panel, enabling session-cookie theft, creation of administrator accounts, installation of malicious plugins, and arbitrary modification of site content.
Published: 2026-07-21
Updated: 2026-07-21
Base Score: 9.4
Vector: CVSS2#AV:N/AC:L/Au:N/C:C/I:C/A:N
Severity: High
Base Score: 9.3
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
Severity: Critical
Base Score: 9.3
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N
Severity: Critical
EPSS: 0.00296