The Happyforms WordPress plugin before 1.26.3 does not sanitise and escape some of its settings, which could allow high privilege users such as admin to perform Stored Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed (for example in multisite setup).
Improper Neutralization of Input During Web Page Generation (XSS or 'Cross-site Scripting') vulnerability in Happyforms allows Stored XSS.This issue affects Happyforms: from n/a through 1.26.0.