YaySMTP <= 2.7.7 - Authenticated (Subscriber+) Arbitrary File Upload via Attachment Filename Extension

The YaySMTP – WP Mail SMTP with Email Logs, Tracking & Reports plugin for WordPress is vulnerable to Arbitrary File Upload in all versions up to, and including, 2.7.7 via the putFile function. This is due to insufficient file type validation in the putFile function, as sanitize_file_name() does not strip executable extensions and no allow-list, MIME check, or safe-extension rename is applied. This makes it possible for authenticated attackers, with subscriber-level access and above, to upload files that may be executable, which makes remote code execution possible. The only server-side guard is a .htaccess file containing 'Require all denied' written by writeGuards(), which is silently ignored by nginx and by Apache configured with AllowOverride None, meaning RCE is fully achievable on those server configurations.

An attacker needs Subscriber access first, so the firewall sees the attempt as traffic from a logged-in account: WordSec's web application firewall inspects request payloads before WordPress loads them. Classes like this one can leave something behind, so the staged malware scanner is the second half: it looks for dropped files and modified code rather than for the request that created them. None of that substitutes for the fix: YaySMTP 2.7.8 closes this, and updating the plugin is the step that ends it.

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