Data sanitization in Wordpress - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to sanitize a text field input in WordPress.

Wordpress

$safe_text = [1]($_POST['user_input']);

Drag options to blanks, or click blank then click option'

Asanitize_text_field

Bwp_kses_post

Cesc_html

Dsanitize_email

Attempts:

3 left

💡 Hint

Common Mistakes

Using esc_html instead of sanitize_text_field for input sanitization.

Using sanitize_email for non-email text fields.

The sanitize_text_field function cleans text input by stripping tags and removing invalid characters, making it safe for storage.

2fill in blank

medium

Complete the code to allow safe HTML tags in user input using WordPress functions.

Wordpress

$allowed_html = array('a' => array('href' => array()));
$safe_html = [1]($_POST['content'], $allowed_html);

Drag options to blanks, or click blank then click option'

Asanitize_text_field

Bwp_kses

Cesc_attr

Dsanitize_email

Attempts:

3 left

💡 Hint

Common Mistakes

Using sanitize_text_field which strips all HTML.

Using esc_attr which escapes for attributes, not sanitizing HTML.

The wp_kses function filters content to allow only specified HTML tags and attributes, preventing harmful code.

3fill in blank

hard

Fix the error in sanitizing an email input in WordPress.

Wordpress

$email = [1]($_POST['email']);

Drag options to blanks, or click blank then click option'

Awp_kses_post

Bsanitize_text_field

Cesc_html

Dsanitize_email

Attempts:

3 left

💡 Hint

Common Mistakes

Using sanitize_text_field which may allow invalid email characters.

Using esc_html which escapes output but does not sanitize input.

The sanitize_email function properly cleans email addresses by removing invalid characters.

4fill in blank

hard

Fill both blanks to sanitize and then escape a URL input safely.

Wordpress

$url = [1]($_POST['website']);
$escaped_url = [2]($url);

Drag options to blanks, or click blank then click option'

Aesc_url_raw

Bsanitize_text_field

Cesc_url

Dsanitize_email

Attempts:

3 left

💡 Hint

Common Mistakes

Escaping before sanitizing input.

Using sanitize_email for URLs.

First, esc_url_raw sanitizes the URL for storage, then esc_url escapes it for safe output in HTML.

5fill in blank

hard

Fill all three blanks to sanitize a checkbox input and safely use it in HTML.

Wordpress

$checked = isset($_POST['agree']) ? [1]($_POST['agree']) : 0;
$checked = $checked ? 1 : 0;
echo '<input type="checkbox"' . ($checked ? ' ' . [2]("checked") : '') . ' />';
$label = '[3]';

Drag options to blanks, or click blank then click option'

Aabsint

Besc_attr

CI agree to terms

Dsanitize_text_field

Attempts:

3 left

💡 Hint

Common Mistakes

Not converting checkbox input to integer.

Not escaping attribute values.

Using unsanitized label text.

Use absint to convert checkbox input to integer 0 or 1, esc_attr to escape the 'checked' attribute value, and a safe label string.

Practice

1. What is the main purpose of data sanitization functions in WordPress?

easy

A. To clean user input and prevent security issues like XSS

B. To speed up database queries

C. To format dates and times for display

D. To compress images before upload

Solution

1. Step 1: Understand data sanitization role

   Data sanitization cleans user input to remove harmful code or characters.

2. Step 2: Identify security benefits

   This prevents attacks like Cross-Site Scripting (XSS) by filtering input.

3. Final Answer:

   To clean user input and prevent security issues like XSS -> Option A

4. Quick Check:

   Data sanitization = Prevent security issues [OK]

Hint: Sanitize input to stop harmful code before saving [OK]

Common Mistakes:

• Confusing sanitization with validation
• Thinking sanitization speeds up queries
• Assuming sanitization formats output

2. Which WordPress function is used to sanitize a text field input?

easy

A. wp_kses_post()

B. esc_html()

C. sanitize_text_field()

D. sanitize_email()

Solution

1. Step 1: Identify function purpose

   sanitize_text_field() cleans plain text input by stripping tags and harmful characters.

2. Step 2: Compare other functions

   esc_html() escapes HTML for output, wp_kses_post() allows safe HTML, sanitize_email() cleans emails.

3. Final Answer:

   sanitize_text_field() -> Option C

4. Quick Check:

   Text field sanitization = sanitize_text_field() [OK]

Hint: Use sanitize_text_field() for plain text inputs [OK]

Common Mistakes:

• Using esc_html() instead of sanitize_text_field() for input
• Confusing sanitize_email() with text sanitization
• Using wp_kses_post() when no HTML is allowed

3. What will be the output of this code snippet?

 $input = "Hello";
$clean = sanitize_text_field($input);
echo $clean;

medium

A. alert('Hi');Hello

B. <script>alert('Hi');</script>Hello

C. alert('Hi');

D. Hello

Solution

1. Step 1: Understand sanitize_text_field() behavior

   This function strips HTML tags and encodes special characters, removing <script> tags.

2. Step 2: Apply to input string

   Input has a script tag and text 'Hello'. After sanitization, only 'Hello' remains.

3. Final Answer:

   Hello -> Option D

4. Quick Check:

   sanitize_text_field() removes tags = Hello [OK]

Hint: sanitize_text_field() removes all HTML tags [OK]

Common Mistakes:

• Expecting script tags to be escaped, not removed
• Confusing sanitize_text_field() with esc_html()
• Thinking output includes script content

4. Identify the error in this code snippet that sanitizes a URL input:

 $url = $_POST['website'];
$clean_url = sanitize_text_field($url);
if (filter_var($clean_url, FILTER_VALIDATE_URL)) {
  echo 'Valid URL';
} else {
  echo 'Invalid URL';
}

medium

A. sanitize_text_field() removes URL characters, causing validation to fail

B. filter_var() is not suitable for URL validation

C. $_POST['website'] should be sanitized with sanitize_email()

D. No error, code works correctly

Solution

1. Step 1: Analyze sanitize_text_field() effect on URL

   This function strips tags and encodes, which can remove or alter URL characters like ':' and '/'.

2. Step 2: Check filter_var() validation

   filter_var() expects a proper URL format, but altered URL fails validation.

3. Final Answer:

   sanitize_text_field() removes URL characters, causing validation to fail -> Option A

4. Quick Check:

   sanitize_text_field() breaks URLs = sanitize_text_field() removes URL characters, causing validation to fail [OK]

Hint: Use esc_url_raw() for URLs, not sanitize_text_field() [OK]

Common Mistakes:

• Using sanitize_text_field() for URLs
• Assuming filter_var() can't validate URLs
• Not sanitizing input before validation

5. You want to save user-submitted HTML content safely in WordPress. Which combination of functions should you use to sanitize and then safely display the content?

hard

A. Use sanitize_text_field() to sanitize and echo with wp_kses_post()

B. Use wp_kses_post() to sanitize and echo with esc_html()

C. Use wp_kses_post() to sanitize and echo directly without escaping

D. Use sanitize_email() to sanitize and echo with esc_attr()

Solution

1. Step 1: Choose sanitizer for HTML content

   wp_kses_post() allows safe HTML tags and removes harmful ones, ideal for user HTML input.

2. Step 2: Escape output for safe display

   Using esc_html() escapes HTML entities to prevent XSS when displaying content.

3. Step 3: Combine sanitization and escaping

   Sanitize input with wp_kses_post(), then escape output with esc_html() for safety.

4. Final Answer:

   Use wp_kses_post() to sanitize and echo with esc_html() -> Option B

5. Quick Check:

   Sanitize HTML input + escape output = Use wp_kses_post() to sanitize and echo with esc_html() [OK]

Hint: Sanitize HTML with wp_kses_post(), escape output with esc_html() [OK]

Common Mistakes:

• Using sanitize_text_field() which strips all HTML
• Echoing sanitized HTML without escaping
• Using sanitize_email() for HTML content