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Introduction:
GraphQL APIs have revolutionized how clients request data, but they also introduce unique attack surfaces. One often overlooked flaw is improper resource deletion when soft delete mechanisms are implemented without validating resource ownership or state. In a recent real‑world finding, an attacker replayed a deleted “PLAYGROUND” creation request and discovered that the old database ID remained reserved—causing the API to return `”was_successful”:false` instead of creating a new resource. This reveals a classic Insecure Direct Object Reference (IDOR) combined with flawed soft delete logic, allowing malicious actors to block resource creation, fingerprint existing IDs, and potentially interfere with business logic.
Learning Objectives:
- Understand how GraphQL mutations can expose IDOR vulnerabilities through soft delete misconfigurations.
- Learn to detect and exploit improper resource deletion using Burp Suite and command‑line tools.
- Implement secure GraphQL deletion patterns with proper access controls and state validation.
You Should Know:
- Understanding the Soft Delete Flaw – Why “Deleted” Resources Still Linger
The vulnerability described follows a typical soft delete pattern: when a user deletes a resource (e.g., a “PLAYGROUND” with ID 1677), the application does not remove the record from the database. Instead, it sets a flag like `deleted_at` or status = 'deleted'. However, the ID sequence remains consumed. When the attacker replays the original creation request (with the same name “Test 2”), the API checks whether that name or ID already exists in a non‑deleted state—or worse, fails to differentiate between soft‑deleted and active records. The result: "was_successful":false.
Step‑by‑step guide to understand the flaw:
- Create a resource normally → gets ID 1677.
- Delete it via the application’s DELETE button (triggers a soft delete mutation).
- Intercept the original creation request (POST to GraphQL endpoint) using Burp Suite.
- Replay that exact request to the Repeater tool.
- Observe the response: instead of ID 1678 (new), you receive a failure message.
- The server still “remembers” ID 1677 as occupied, but the resource is invisible to normal users.
Linux command to test with cURL (after capturing the request):curl -X POST https://target.com/graphql \ -H "Content-Type: application/json" \ -H "Authorization: Bearer <token>" \ -d '{"query":"mutation { createPlayground(name: \"Test 2\") { id name } }"}' -
Recreating the IDOR Attack on GraphQL – Burp Suite Deep Dive
The attack leverages replayed mutations after soft deletion. Because GraphQL endpoints often lack per‑request nonce or state validation, an attacker can resend a legitimate request that the server incorrectly processes against a deleted resource.
Step‑by‑step exploitation guide:
- Intercept creation – Turn on Burp Suite proxy, create a new “PLAYGROUND” with name “Test 2”. Forward the request to Repeater (Ctrl+R).
- Delete the resource – Use the application’s DELETE function. Capture that deletion request as well to understand the mutation.
- Replay the creation – In Repeater, resend the original `createPlayground` mutation.
- Analyze response – Look for error codes like `”was_successful”:false` or GraphQL `errors` array indicating duplication.
- Fuzz ID parameters – If the mutation accepts an `id` argument (e.g.,
updatePlayground(id: 1677)), try modifying it to other users’ deleted IDs.
Windows command (PowerShell) example:
$body = '{"query":"mutation { deletePlayground(id: 1677) { success } }"}'
Invoke-RestMethod -Uri "https://target.com/graphql" -Method Post -Body $body -ContentType "application/json"
6. Confirm IDOR – If you can delete or manipulate a resource that belongs to another user (or one that is already soft‑deleted), the vulnerability is confirmed.
- Exploiting GraphQL with Command Line – cURL & GraphQL Introspection
Many GraphQL APIs expose introspection, allowing you to discover mutations. Combine this with the soft‑delete IDOR to enumerate reserved IDs.
Step‑by‑step command‑line attack:
1. Discover mutations (if introspection is enabled):
curl -X POST https://target.com/graphql -H "Content-Type: application/json" -d '{"query":"{ __schema { mutationType { fields { name } } } }"}'
2. Attempt to create a resource with a known deleted ID (if the mutation allows specifying ID):
curl -X POST https://target.com/graphql -d '{"query":"mutation { createPlayground(id: 1677, name: \"Test 2\") { id } }"}'
3. Burst test ID range – Use a bash loop to check which IDs return false:
for id in {1670..1680}; do
curl -s -X POST https://target.com/graphql -H "Content-Type: application/json" \
-d "{\"query\":\"mutation { checkId(id: $id) { exists } }\"}" | grep -q "false" && echo "ID $id is blocked"
done
4. Abuse as a denial‑of‑resource – By replaying creation requests for many soft‑deleted names, you can exhaust the namespace and prevent legitimate users from creating new resources.
- Mitigation Strategies – Hard Delete vs. Soft Delete with Validation
Soft delete is convenient for recovery and auditing, but it must be paired with strict ownership checks and unique constraints that exclude deleted records. The root cause here is that the GraphQL resolver did not filter out soft‑deleted resources when validating uniqueness.
Step‑by‑step secure implementation:
- Database level – Create a partial unique index (PostgreSQL example):
CREATE UNIQUE INDEX idx_active_playground_name ON playgrounds (name) WHERE deleted_at IS NULL;
- GraphQL resolver logic – Before creating a resource, check if an active record exists:
const existing = await db.playground.findOne({ where: { name: args.name, deleted_at: null } }); if (existing) throw new Error("Name already in use by an active playground"); - Hard delete for sensitive resources – If no recovery needed, delete permanently:
DELETE FROM playgrounds WHERE id = $1 AND user_id = $2 RETURNING ;
- Enforce IDOR prevention – Always validate that the authenticated user owns the resource before any operation (create, read, update, delete).
Example middleware in Node.js:
if (resource.user_id !== req.user.id) return forbidden();
5. Rate limit replay attacks – Implement request throttling on GraphQL mutations, especially creation and deletion.
5. Secure GraphQL API Hardening – Complete Checklist
To prevent the exact flaw (IDOR + improper soft delete), harden your GraphQL endpoint with these controls:
Step‑by‑step hardening guide:
- Disable introspection in production – Use tools like `graphql-disable-introspection` or gateway rules.
- Implement persisted queries – Allow only pre‑approved mutations.
- Add CSRF tokens – GraphQL requests over GET are dangerous; use POST with anti‑CSRF headers.
- Validate input depth and aliases – Prevent batch attacks that could loop over deleted IDs.
- Log soft‑delete events – Monitor for repeated `”was_successful”:false` responses; they indicate replay attempts.
- Linux command to monitor logs in real time:
tail -f /var/log/graphql/access.log | grep "was_successful.false"
7. Windows PowerShell alternative:
Get-Content -Path "C:\logs\graphql.log" -Wait | Select-String "was_successful"
What Undercode Say:
- Key Takeaway 1: Soft delete is not a security boundary. Without proper validation (e.g., partial unique indexes, ownership checks), attackers can replay requests to block resource creation or fingerprint internal IDs.
- Key Takeaway 2: GraphQL’s flexibility amplifies IDOR risks because clients can specify exactly which fields and mutations to call. Always treat user‑supplied IDs as untrusted and enforce row‑level security.
Analysis: This low‑severity finding is a classic example of how business logic flaws hide behind “soft delete” convenience. While the impact may be limited to denial of service or minor information disclosure, it often chains with other bugs (e.g., IDOR on update mutations) to become critical. Many developers assume that deleting a resource removes it entirely from the API’s perspective, but databases retain records. The core lesson: never rely on client‑side deletion status; validate server‑side whether a resource is truly active and owned by the requester. Tools like Burp Suite’s Repeater and cURL make such replay attacks trivial—so automated testing for replay vulnerabilities should be part of every GraphQL CI/CD pipeline.
Prediction:
As GraphQL adoption grows, we will see a surge in “soft delete IDOR” vulnerabilities, especially in microservices where developers copy‑paste soft‑delete patterns from REST without adapting them to GraphQL’s persistent query nature. Attackers will automate replay attacks using tools like InQL (Burp GraphQL extension) to scan for mutations that return inconsistent state messages. In the next 12 months, expect bug bounty programs to raise the severity of such issues from Low to Medium, as chained attacks (e.g., replay creation + IDOR on update) enable full account takeover. Defenders will shift toward immutable data stores for audit logs and adopt GraphQL‑specific security linters that flag mutations lacking state validation. The future of API security lies not in blocking obvious injections but in modeling business logic state machines—and soft delete is a prime candidate for the next wave of automated exploit generators.
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IT/Security Reporter URL:
Reported By: Sans1986 Idor – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
