The No External Links plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Log URL via /goto/{base64} Redirect in all versions up to, and including, 5.2.0 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This is only exploitable when the administrator has enabled the 'Link Encoding: Base64' option in the plugin settings.