Postie <= 1.9.87 - Unauthenticated Stored Cross-Site Scripting via Email Body URL Autolink

The Postie plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Email Body URL Autolink in all versions up to, and including, 1.9.87 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 possible because the ?postie=get-mail endpoint is reachable by unauthenticated users with no capability check, and the email processing path removes WordPress's kses output filters before saving raw markup, allowing the unescaped href attribute value to be stored as post content.