Ultimate Posts Widget < 2.3.1 - Admin+ Stored XSS

Description The plugin does not validate and escape some of its Widget options before outputting them back in attributes, 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)

PoC

As admin, create/edit an Ultimate Post widget and put the following payload in the Title, URL or “CSS Classes” fields: " onmouseover=“alert(/XSS/)” The XSS will be triggered when a user move their mouse over - the title of the widget on page where the widget is output - the related field when editing the widget Other payload, for the URL field to trigger in the frontend: ’ onmouseover=alert(/XSS-URL/)// and javascript:alert(/XSS/)