Authentication vulnerability testing in Testing Fundamentals - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Common Weakness in Authentication Systems

Which of the following is the most common authentication vulnerability that allows attackers to bypass login without valid credentials?

A SQL Injection in login form

B Cross-Site Scripting (XSS) in user profile

C Insecure Direct Object Reference (IDOR) in file access

D Open Redirect in logout URL

💡 Hint

Think about how attackers can trick the system into accepting wrong usernames or passwords.

SQL Injection in login forms can allow attackers to manipulate database queries to bypass authentication checks.

❓ Predict Output

intermediate

Output of Authentication Check Code

What is the output of the following Python code simulating a simple password check?

Testing Fundamentals

def check_password(input_password):
    stored_password = 'Pass1234'
    if input_password.lower() == stored_password.lower():
        return 'Access Granted'
    else:
        return 'Access Denied'

print(check_password('pass1234'))

A TypeError

B Access Granted

C Access Denied

D SyntaxError

💡 Hint

Check how the comparison is done with lower() method.

The code compares passwords ignoring case, so 'pass1234' matches 'Pass1234' and grants access.

❓ assertion

advanced

Correct Assertion for Password Length Validation

Which assertion correctly tests that a password string has at least 8 characters?

Testing Fundamentals

password = 'securePass'
# Choose the correct assertion below

A assert password.size >= 8

B assert password.length > 8

C assert len(password) > 8

D assert len(password) >= 8

💡 Hint

Remember Python uses len() function and >= means 'at least'.

Option D uses correct Python syntax and checks for minimum length 8 correctly.

🔧 Debug

advanced

Identify the Bug in Authentication Code

What is the bug in this JavaScript authentication snippet?

Testing Fundamentals

function authenticate(userInput) {
  const password = 'Secret!';
  if (userInput === password) {
    return 'Logged In';
  } else {
    return 'Access Denied';
  }
}
console.log(authenticate('Secret!'));

A Uses assignment (=) instead of comparison (===) in if condition

B Password variable is not declared properly

C Function does not return any value

D Console.log syntax is incorrect

💡 Hint

Check the if condition operator carefully.

The if condition uses '=' which assigns instead of comparing, causing always true and wrong logic.

❓ framework

expert

Best Practice for Testing Authentication Rate Limiting

Which testing approach best verifies that an authentication system properly limits login attempts to prevent brute force attacks?

A Test password reset functionality for valid email

B Manually enter correct password once and verify access

C Automate rapid login attempts with invalid passwords and check for lockout response

D Check UI layout of login page on mobile devices

💡 Hint

Think about how to simulate many wrong tries quickly.

Automated rapid invalid login attempts test if the system blocks further tries, protecting against brute force.

Practice

1. What is the main goal of authentication vulnerability testing?

easy

A. To ensure only authorized users can access the system

B. To check the system's speed under heavy load

C. To verify the user interface design

D. To test database backup procedures

Solution

1. Step 1: Understand authentication testing purpose

   Authentication testing focuses on verifying that only real, authorized users can access the system.

2. Step 2: Eliminate unrelated options

   Options about speed, UI, or backups do not relate to authentication vulnerabilities.

3. Final Answer:

   To ensure only authorized users can access the system -> Option A

4. Quick Check:

   Authentication goal = authorized access [OK]

Hint: Authentication testing checks who can enter the system [OK]

Common Mistakes:

• Confusing authentication with performance testing
• Thinking authentication tests UI elements
• Mixing authentication with data backup checks

2. Which of the following is a correct way to test for weak password acceptance during authentication?

easy

A. Try logging in with a password like 12345

B. Check if the system allows SQL queries in the username field

C. Test if the login page loads within 2 seconds

D. Verify if the password reset email is sent

Solution

1. Step 1: Identify weak password test

   Testing weak passwords means trying simple, common passwords like '12345' to see if the system accepts them.

2. Step 2: Differentiate from other tests

   Options about SQL injection, performance, or email sending are different security or functionality tests.

3. Final Answer:

   Try logging in with a password like 12345 -> Option A

4. Quick Check:

   Weak password test = simple password try [OK]

Hint: Use simple passwords to check weak password acceptance [OK]

Common Mistakes:

• Confusing weak password test with SQL injection test
• Testing page speed instead of authentication strength
• Mixing password reset with password strength testing

3. Consider this pseudocode for testing login lockout:

attempts = 0
while attempts < 5:
    login('user', 'wrongpass')
    attempts += 1
result = login('user', 'correctpass')

What should result be if the system locks the account after 5 failed attempts?

medium

A. Login successful

B. Account locked error

C. Password reset prompt

D. System crash

Solution

1. Step 1: Understand lockout after failed attempts

   After 5 wrong tries, the system should lock the account to prevent further access.

2. Step 2: Analyze final login attempt

   Even with the correct password, the account is locked, so login should fail with an account locked error.

3. Final Answer:

   Account locked error -> Option B

4. Quick Check:

   Lockout after 5 fails = account locked error [OK]

Hint: After 5 fails, login should block even correct passwords [OK]

Common Mistakes:

• Expecting login success after lockout
• Confusing reset prompt with lockout error
• Assuming system crashes on failed login

4. You wrote this test to check multi-factor authentication (MFA):

login('user', 'correctpass')
// skip MFA step
access = check_access()

Why might this test fail to detect an authentication vulnerability?

medium

A. It uses the wrong username format

B. It checks access before login

C. It tests password reset instead of login

D. It skips the MFA step, so it doesn't test full authentication

Solution

1. Step 1: Identify skipped MFA step

   The test logs in with correct password but skips the MFA step, missing a critical security check.

2. Step 2: Understand impact on vulnerability detection

   Skipping MFA means the test won't catch if MFA is bypassed, leaving a vulnerability undetected.

3. Final Answer:

   It skips the MFA step, so it doesn't test full authentication -> Option D

4. Quick Check:

   Skipping MFA = incomplete authentication test [OK]

Hint: Always include MFA step to test full authentication [OK]

Common Mistakes:

• Ignoring MFA step importance
• Confusing username format with MFA issues
• Mixing login and password reset tests

5. You want to test if the system properly prevents session fixation attacks after login. Which test approach is best?

hard

A. Verify if password reset emails are sent promptly

B. Try logging in with an invalid password multiple times

C. Check if session ID changes after successful login

D. Test if the login page uses HTTPS

Solution

1. Step 1: Understand session fixation attack

   Session fixation means attacker forces a known session ID before login to hijack session.

2. Step 2: Identify test to prevent session fixation

   The system should assign a new session ID after login to prevent fixation.

3. Final Answer:

   Check if session ID changes after successful login -> Option C

4. Quick Check:

   Session fixation test = session ID change after login [OK]

Hint: Session ID must change after login to stop fixation [OK]

Common Mistakes:

• Confusing session fixation with password errors
• Testing unrelated password reset or HTTPS only
• Ignoring session ID behavior after login