Page Builder: Pagelayer < 2.0.9 - Authenticated (Contributor+) Stored Cross-Site Scripting via Button Widget Custom Attributes

Description

The Page Builder: Pagelayer plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the Button widget's Custom Attributes field in all versions up to, and including, 2.0.8. This is due to an incomplete event handler blocklist in the 'pagelayer_xss_content' XSS filtering function, which blocks common, but not all, event handlers. This makes it possible for authenticated attackers, with Contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.