The SiteOrigin CSS plugin for WordPress is vulnerable to Stored DOM-Based Cross-Site Scripting via the 'href' parameter in all versions up to, and including, 1.6.7 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. Successful exploitation requires the malicious comment to be approved and an administrator to subsequently open the Visual Inspector and click the attacker's anchor link, both of which are plausible interactions during routine comment triage.