Simply Schedule Appointments < 1.5.7.7 - Admin+ Stored Cross-Site Scripting

The plugin 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)

PoC

Navigate to style settings: https://example.com/wp-admin/admin.php?page=simply-schedule-appointments%2F#/ssa/settings/styles Put the following payload as “CUSTOM CSS”: alert(1)