The Plugin Oficial WordPress plugin through 1.7.3 does not sanitise and escape a parameter before outputting it back in the page, leading to a Reflected Cross-Site Scripting which could be used against only unauthenticated users.
The Plugin Oficial WordPress plugin through 1.7.3 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).