The Ivory Search – WordPress Search Plugin plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the 's' parameter in all versions up to, and including, 5.5.18 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. Exploitation requires that the targeted search form has the 'Highlight Search Terms' option enabled by an administrator, and that the malicious search query returns at least one post result.