In the process of testing the MailPoet WordPress plugin before 5.3.2, a vulnerability was found that allows you to implement Stored XSS on behalf of the editor by embedding malicious script, which entails account takeover backdoor
The MailPoet – Newsletters, Email Marketing, and Automation plugin for WordPress is vulnerable to Stored Cross-Site Scripting via admin settings in all versions up to, and including, 5.3.1 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with administrator-level permissions and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This only affects multi-site installations and installations where unfiltered_html has been disabled.
