The ElasticPress plugin for WordPress is vulnerable to Cross-Site Request Forgery in versions up to, and including, 3.5.3. This is due to missing or incorrect nonce validation on the epio_send_autosuggest_allowed() function. This makes it possible for unauthenticated attackers to send allowed parameters for autosuggest to elasticpress[.]io via a forged request granted they can trick a site administrator into performing an action such as clicking on a link.