Despite "Allow Guest Checkout" set to "No" it's possible to place a guest order with the guest-carts REST API

[C4rter]

Preconditions and environment

• Magento 2.4.4 and 2.4.5-p1

We just had a hacker that tried to use the vulnerability "APSB22-12" to hack our store.

Thankfully we had the patches applied on 2.4.4 (and now upgraded to 2.4.5-p1) and he was not successful.
But he was able to try out the vulnerability by placing a guest order via the Rest API despite the guest-checkout being disabled in the backend.

Why is this still possible via API? It's a big risk because it allows unwanted guest orders being placed and in my case letting a hacker try out vulnerabilities.

How do I know that he did it via API?
There is no way to place a guest order via the frontend and you can see it in the access log how he did it:

"POST /checkout/cart/add/uenc/aHR0cHM6Ly93d3cucGxhdGV3cml0ZS5kZS9jdHAtZHJ1Y2twbGF0dGVuYmVsaWNodHVuZy9kcnVja3BsYXR0ZS0yNTB4MzcwLmh0bWw%2C/product/500/ HTTP/1.1" 200 1025 "-"
"GET /checkout HTTP/1.1" 302 1388 "-"
"GET /checkout/cart/ HTTP/1.1" 200 34064 "-"
"POST /rest/default/V1/customers/isEmailAvailable HTTP/1.1" 400 354 "-"
"POST /rest/italian/V1/customers/isEmailAvailable HTTP/1.1" 400 4619 "-"
"POST /rest/de/V1/customers/isEmailAvailable HTTP/1.1" 200 4840 "-"
"POST /rest/de/V1/guest-carts/Qgfa1jFEf8m430Vlo0xnFLz2uIyqAUPI/estimate-shipping-methods HTTP/1.1" 200 1021 "-"
"POST /rest/de/V1/guest-carts/Qgfa1jFEf8m430Vlo0xnFLz2uIyqAUPI/shipping-information HTTP/1.1" 200 3374 "-"
"POST /rest/de/V1/guest-carts/Qgfa1jFEf8m430Vlo0xnFLz2uIyqAUPI/payment-information HTTP/1.1" 200 4843 "-"
"POST /b2b.php HTTP/1.1" 302 5380 "-"

At the end he even tries to call the b2b.php file that he tried to create with his injection.

Steps to reproduce

1. Make sure "Allow Guest Checkout" is set to "No" in Backend Config (Stores->Configuration->Sales->Checkout->Allow Guest Checkout)
2. Check if guest checkout is possible when going through the frontend (should not and is not possible)
3. Do a guest-checkout with the use of the Rest API.

Get a new Cart:
POST https://[YOUR-SHOP-URL]/rest/[YOUR-STORE-VIEW-CODE]/V1/guest-carts
You receive a basket ID here that you need in every step.

Add a product to the Cart:
POST https://[YOUR-SHOP-URL]/rest/[YOUR-STORE-VIEW-CODE]/V1/guest-carts/[YOUR-BASKET-ID]/items

Body:

{
  "cartItem": {
    "sku": "[SOME-EXISTING-SKU]",
    "qty": 1
  }
}

Set shipping and billing address:
POST https://[YOUR-SHOP-URL]/rest/[YOUR-STORE-VIEW-CODE]/V1/guest-carts/[YOUR-BASKET-ID]/shipping-information

Body:
(Make sure you use a shipping method that exists. Maybe adjust the country to one that's allowed in your setup.)

{
  "addressInformation": {
    "shipping_address": {
      "region": "New York",
      "region_id": 0,
      "region_code": "",
      "country_id": "DE",
      "street": [
        "123 Oak Ave"
      ],
      "postcode": "10577",
      "city": "Purchase",
      "firstname": "Jane",
      "lastname": "Doe",
      "email": "jdoe@example.com",
      "telephone": "512-555-1111"
    },
    "billing_address": {
      "region": "New York",
      "region_id": 0,
      "region_code": "",
      "country_id": "DE",
      "street": [
        "123 Oak Ave"
      ],
      "postcode": "10577",
      "city": "Purchase",
      "firstname": "Jane",
      "lastname": "Doe",
      "email": "jdoe@example.com",
      "telephone": "512-555-1111"
    },
    "shipping_carrier_code": "freeshipping",
    "shipping_method_code": "freeshipping"
  }
}

Place Order:
POST https://[YOUR-SHOP-URL]/rest/[YOUR-STORE-VIEW-CODE]/V1/guest-carts/[YOUR-BASKET-ID]/payment-information

Body:
(You will have to adjust the agreement IDs or leave them out entirely and make sure you use a payment method that exists)

{
  "email": "jdoe@example.com",
  "paymentMethod": {
    "method": "banktransfer",
    "extension_attributes": {"agreement_ids": ["1","2","5"]}
  },
  "billing_address": {
    "email": "jdoe@example.com",
    "region": "New York",
    "region_id": 0,
    "region_code": "",
    "country_id": "DE",
    "street": [
      "123 Oak Ave"
    ],
    "postcode": "10577",
    "city": "Purchase",
    "telephone": "512-555-1111",
    "firstname": "Jane",
    "lastname": "Doe",
    "same_as_billing": 0
  }
}

4. Guest Order will be placed.

Expected result

Guest checkout should not be possible via the API when the guest checkout is disabled in the configuration.

Actual result

Guest checkout can be used and an order can be placed as a guest.

Additional information

Maybe somewhere in vendor/magento/module-checkout/Model/GuestPaymentInformationManagement.php in the savePaymentInformationAndPlaceOrder function there can be a condition, that checks if guest checkout is even allowed.

Release note

No response

Triage and priority

• Severity: S0 - Affects critical data or functionality and leaves users without workaround.
• Severity: S1 - Affects critical data or functionality and forces users to employ a workaround.
• Severity: S2 - Affects non-critical data or functionality and forces users to employ a workaround.
• Severity: S3 - Affects non-critical data or functionality and does not force users to employ a workaround.
• Severity: S4 - Affects aesthetics, professional look and feel, “quality” or “usability”.

[m2-assistant]

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[engcom-Bravo]

@magento give me 2.4-develop instance

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[engcom-Bravo]

Hi @C4rter,

Thank you for reporting and collaboration.
Verified the issue on Magento 2.4-develop instance and the issue is not reproducible.Kindly refer the screenshots.

Using frontend not able to place the order as a Guest.

Using API not able to place the order as a Guest.

Kindly let us know if we miss anything.

Thanks.

[viktorlantos]

The same thing happened to us a few days ago on 2.4.5-p1. Guest checkout was set as NO. Pretty worrying.

[C4rter]

Hi @engcom-Bravo

thank you for testing. As I see from your screenshots you used the GraphQL endpoint.
I mentioned that the hacker used the REST API endpoint and my "Steps to reproduce" also show the Rest API.

It might be that it's not possible via the GraphQL endpoint but I'm sure it's possible via the Rest API.

The error that's visible in your screenshot is a GQL specific error, thrown in a file only used when using the GQL API:
vendor/magento/module-quote-graph-ql/Model/Cart/CheckCartCheckoutAllowance.php

    public function execute(Quote $quote): void
    {
        if (!$quote->getCustomerIsGuest()) {
            return;
        }

        $isAllowedGuestCheckout = (bool)$this->checkoutHelper->isAllowedGuestCheckout($quote);
        if (false === $isAllowedGuestCheckout) {
            throw new GraphQlAuthorizationException(
                __(
                    'Guest checkout is not allowed. ' .
                    'Register a customer account or login with existing one.'
                )
            );
        }
    }

So it makes sense, that it's not possible when using GQL Api. But it's unfortunately possible when using REST API.

Can you please verify it via the REST API endpoint?
Thanks

[viktorlantos]

To confirm, we had Rest API guest order as well. Just finished the Sansec scan, and with M2.4.5-p1 only the order was placed. No other harm was detected. Sansec Scrutinize mode found it in the db:quote
10% MALWARE m2_template_attack_payload_cc6e3

[engcom-Bravo]

Hi @C4rter,

Thanks for your update.

@viktorlantos Thanks for your contribution & collaboration over here.

Verified the issue on Magento 2.4-develop instance and the issue is reproducible.Kindly refer the screenshots.

Steps to reproduce
1.Make sure "Allow Guest Checkout" is set to "No" in Backend Config (Stores->Configuration->Sales->Checkout->Allow Guest Checkout)
2.Check if guest checkout is possible when going through the frontend (should not and is not possible)
3.Do a guest-checkout with the use of the Rest API.

Using frontend we are not able to place the order as a guest.

Using Rest Api we are able to place the order as a guest.

Hence confirming this issue.

Thanks.