Registration & Takeover Vulnerabilities

Registration Takeover

Duplicate Registration

  • Try to generate using an existing username
  • Check varying the email:

Username Enumeration

Check if you can figure out when a username has already been registered inside the application.

Password Policy

Creating a user check the password policy (check if you can use weak passwords). In that case you may try to bruteforce credentials.

SQL Injection

Check this page to learn how to attempt account takeovers or extract information via SQL Injections in registry forms.

Oauth Takeovers

SAML Vulnerabilities

Change Email

when registered try to change the email and check if this change is correctly validated or can change it to arbitrary emails.

More Checks

  • Check if you can use disposable emails
  • Long password (>200) leads to DoS
  • Check rate limits on account creation
  • Use and analyze the callback

Password Reset Takeover

Password Reset Token Leak Via Referrer

  1. 1.
    Request password reset to your email address
  2. 2.
    Click on the password reset link
  3. 3.
    Don’t change password
  4. 4.
    Click any 3rd party websites(eg: Facebook, twitter)
  5. 5.
    Intercept the request in Burp Suite proxy
  6. 6.
    Check if the referer header is leaking password reset token.

Password Reset Poisoning

  1. 1.
    Intercept the password reset request in Burp Suite
  2. 2.
    Add or edit the following headers in Burp Suite : Host:, X-Forwarded-Host:
  3. 3.
    Forward the request with the modified header http POST HTTP/1.1 Accept: */* Content-Type: application/json Host:
  4. 4.
    Look for a password reset URL based on the host header like :

Password Reset Via Email Parameter

# parameter pollution
# array of emails
# carbon copy
# separator,|

IDOR on API Parameters

  1. 1.
    Attacker have to login with their account and go to the Change password feature.
  2. 2.
    Start the Burp Suite and Intercept the request
  3. 3.
    Send it to the repeater tab and edit the parameters : User ID/email powershell POST /api/changepass [...] ("form": {"email":"vic[email protected]","password":"securepwd"})

Weak Password Reset Token

The password reset token should be randomly generated and unique every time. Try to determine if the token expire or if it’s always the same, in some cases the generation algorithm is weak and can be guessed. The following variables might be used by the algorithm.
  • Timestamp
  • UserID
  • Email of User
  • Firstname and Lastname
  • Date of Birth
  • Cryptography
  • Number only
  • Small token sequence ( characters between [A-Z,a-z,0-9])
  • Token reuse
  • Token expiration date

Leaking Password Reset Token

  1. 1.
    Trigger a password reset request using the API/UI for a specific email e.g: [email protected]
  2. 2.
    Inspect the server response and check for resetToken
  3. 3.
    Then use the token in an URL like[THE_RESET_TOKEN]&email=[THE_MAIL]

Password Reset Via Username Collision

  1. 1.
    Register on the system with a username identical to the victim’s username, but with white spaces inserted before and/or after the username. e.g: "admin "
  2. 2.
    Request a password reset with your malicious username.
  3. 3.
    Use the token sent to your email and reset the victim password.
  4. 4.
    Connect to the victim account with the new password.
The platform CTFd was vulnerable to this attack. See: CVE-2020-7245

Account Takeover Via Cross Site Scripting

  1. 1.
    Find an XSS inside the application or a subdomain if the cookies are scoped to the parent domain : *
  2. 2.
    Leak the current sessions cookie
  3. 3.
    Authenticate as the user using the cookie

Account Takeover Via HTTP Request Smuggling

1. Use smuggler to detect the type of HTTP Request Smuggling (CL, TE, CL.TE) powershell git clone cd smuggler python3 -h 2. Craft a request which will overwrite the POST / HTTP/1.1 with the following data: GET HTTP/1.1 X: with the goal of open redirect the victims to burpcollab and steal their cookies 3. Final request could look like the following
GET / HTTP/1.1
Transfer-Encoding: chunked
User-Agent: Smuggler/v1.0
Content-Length: 83
X: X

Account Takeover via CSRF

  1. 1.
    Create a payload for the CSRF, e.g: “HTML form with auto submit for a password change”
  2. 2.
    Send the payload

Account Takeover via JWT

JSON Web Token might be used to authenticate an user.
  • Edit the JWT with another User ID / Email
  • Check for weak JWT signature