Data sanitization in Wordpress - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is data sanitization in WordPress?

Data sanitization in WordPress means cleaning user input to remove harmful or unwanted code before saving or using it. It helps keep the site safe from attacks.

beginner

Which WordPress function is used to sanitize text fields?

The function sanitize_text_field() cleans text input by stripping tags and removing harmful characters.

beginner

Why should you sanitize data before saving it in WordPress?

Sanitizing data prevents malicious code from entering your database, protects users, and keeps your site secure.

intermediate

What is the difference between sanitization and validation in WordPress?

Sanitization cleans data to make it safe, while validation checks if data meets certain rules or formats before processing.

intermediate

Name two WordPress functions used for sanitizing URLs and emails.

Use esc_url_raw() to sanitize URLs and sanitize_email() to clean email addresses.

Which function should you use to sanitize a plain text input in WordPress?

A sanitize_email()

B wp_kses_post()

C esc_html()

D sanitize_text_field()

sanitize_text_field() is designed to clean plain text inputs by removing tags and harmful characters.

What does data sanitization help prevent in WordPress sites?

A Malicious code injection

B Faster page loading

C Better SEO ranking

D More user comments

Sanitization helps prevent malicious code injection that can harm your site or users.

Which function is best for sanitizing an email address in WordPress?

A esc_url()

B sanitize_text_field()

C sanitize_email()

D wp_strip_all_tags()

sanitize_email() cleans and validates email addresses to ensure they are safe.

What is the main difference between sanitization and validation?

A Sanitization cleans data; validation checks data format

B Sanitization checks data format; validation cleans data

C Both do the same thing

D Sanitization is only for numbers

Sanitization cleans data to make it safe, while validation checks if data fits expected rules.

Which function would you use to allow safe HTML tags in user input?

A sanitize_text_field()

B wp_kses_post()

C sanitize_email()

D esc_url()

wp_kses_post() allows safe HTML tags while removing harmful ones.

Explain why data sanitization is important in WordPress and name three functions used for it.

Think about how bad input can harm your site and which functions clean different types of data.

Describe the difference between sanitization and validation in WordPress with examples.

One makes data safe, the other makes sure data is correct.

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