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The Broken Link Notifier WordPress plugin before 2.0.0.1 does not re-validate the destination of redirects when checking links, allowing unauthenticated attackers to bypass its internal-address filter and make the server send requests to internal services.
The Broken Link Notifier plugin for WordPress is vulnerable to Server-Side Request Forgery in all versions up to, and including, 1.3.0 via the ajaxblinks() function which ultimately calls the checkurlstatuscode() function. This makes it possible for unauthenticated attackers to make web requests to arbitrary locations originating from the web application and can be used to query and modify information from internal services.