WebberZone Top 10 < 4.5.3 - Authenticated (Contributor+) Stored Cross-Site Scripting via 'other_attributes' Block Attribute

Description

The WebberZone Top 10 — Popular Posts plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'other_attributes (parsed to inject instance_id) + undeclared is_widget' parameter in all versions up to, and including, 4.5.2 due to insufficient input sanitization and output escaping. 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. The exploit requires setting the undeclared is_widget flag to '1' via block JSON, which activates the vulnerable code path that concatenates the attacker-controlled instance_id value into an unescaped HTML class attribute.