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Prevent XSS attacks on your WordPress site

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Cross-Site Scripting or (XSS) is a common web security vulnerability where malicious scripts are injected into a website.

WordPress Sanitizing

Sanitizing user input is crucial in WordPress to prevent security vulnerabilities like cross-site scripting (XSS), SQL injection, and cross-site request forgery (CSRF). 

By sanitizing data before it’s used in queries or displayed on the frontend, you protect your website and its users from malicious attacks.

$username = sanitize_text_field( $_POST['username'] );
$email = sanitize_email( $_POST['email'] );

Never trust user input and never assume anything. Validation on the client-side is for the user’s benefit; validation/sanitization on the server-side is always needed.

Let me show you with this example

Lets say we have a input field with Name, Email & Message, a basic contact form…

<input id="name" type="text" name="cName">
<input id="email" type="text" name="cEmail">
<textarea id="message" name="cMessage"></textarea>

We now have to sanitize the input data with the sanitize_text_field(), sanitize_email() and sanitize_textarea_field() functions.

$name = sanitize_text_field( $_POST['cName'] );
$name = sanitize_email( $_POST['cEmail'] );
$name = sanitize_textarea_field( $_POST['cMessage'] );

Behind the scenes, sanitize_text_field() does the following:

  1. Checks for invalid UTF-8
  2. Converts single less-than characters (<) to entity
  3. Strips all tags
  4. Removes line breaks, tabs and extra white space
  5. Strips octets

The sanitize_textarea_field() is like the sanitize_text_field(), but preserves new lines (\n) and other whitespace, which are legitimate input in textarea elements.

And the sanitize_email() uses a smaller allowable character set than the set defined by RFC 5322.

sanitize_email() filter is evaluated under several contexts, including ’email_too_short’, ’email_no_at’, ‘local_invalid_chars’, ‘domain_period_sequence’, ‘domain_period_limits’, ‘domain_no_periods’, ‘domain_no_valid_subs’, or no context.

Remember: Even admins are users, and users will enter incorrect data, either on purpose or accidentally. It’s your job to protect them from themselves.

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