Description
The WordPress plugin "MailPoet Newsletters" (wysija-newsletters) before version 2.6.8 is vulnerable to an unauthenticated file upload. An attacker can use the Upload Theme functionality to upload a zip file containing a PHP shell.
Remediation
Upgrade to the latest version of MailPoet Newsletters (this issue was fixed in version 2.6.8).
References
MailPoet Newsletters Changelog
Remote File Upload Vulnerability in WordPress MailPoet Plugin (wysija-newsletters)
WordPress MailPoet Newsletters (wysija-newsletters) Unauthenticated File Upload
Related Vulnerabilities
WordPress Plugin Simple:Press Security Bypass and Arbitrary File Upload Vulnerabilities (4.1.2)
WordPress Plugin Kish Guest Posting 'uploadify.php' Arbitrary File Upload (1.2)
WordPress Plugin WordPress Backup and Migrate-Backup Guard Arbitrary File Upload (1.5.9)