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Edit File: class-wc-helper-sanitization.php

<?php
/**
 * WooCommerce Admin Sanitization Helper
 *
 * @package WooCommerce\Admin\Helper
 */

declare(strict_types=1);

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * WC_Helper_Sanitization Class
 *
 * Provides sanitization functions for admin content.
 */
class WC_Helper_Sanitization {

/**
	 * Sanitize CSS markup from API responses for safe rendering in admin pages.
	 *
	 * @param string $css The raw CSS to sanitize.
	 *
	 * @return string Sanitized CSS safe for inclusion in style blocks.
	 */
	public static function sanitize_css( $css ) {
		// Handle non-string inputs (return empty string).
		if ( ! is_string( $css ) ) {
			return '';
		}

// Remove potentially harmful constructs.
		$css = preg_replace( '/@import\s+[^;]+;?/', '', $css );

// Block all data URIs.
		$css = preg_replace( '/url\s*\(\s*([\'"]?)data:/i', 'url($1invalid:', $css );

// Only allow URLs from specific trusted domains and their subdomains.
		$css = preg_replace_callback(
			'/url\s*$\s*([\'"]?)(https?:\/\/[^)]+)\1\s*$/i',
			function ( $matches ) {
				$url   = $matches[2];
				$quote = $matches[1];

// Check if URL belongs to allowed domains.
				if ( preg_match(
					'/^https?:\/\/(([\w-]+\.)*woocommerce\.com|' .
					'([\w-]+\.)*woocommerce\.test|' .
					'([\w-]+\.)*WordPress\.com|' .
					'([\w-]+\.)*wp\.com)/ix',
					$url
				) ) {
					// URL is from a trusted domain, keep it.
					return "url({$quote}{$url}{$quote})";
				} else {
					// URL is not from a trusted domain, make it ineffective.
					return "url({$quote}#blocked-url{$quote})";
				}
			},
			$css
		);

// Preserve all asterisks by temporarily replacing them.
		$css = str_replace( '*', '__PRESERVED_ASTERISK__', $css );

// Remove HTML tags and PHP.
		$css = wp_strip_all_tags( $css );

// Remove any JavaScript events.
		$css = preg_replace( '/\s*expression\s*$.*?$/', '', $css );
		$css = preg_replace( '/\s*javascript\s*:/', '', $css );

// Block other potentially dangerous protocols.
		$css = preg_replace( '/(behavior|eval|calc|mocha)(\s*:|\s*\()/i', 'blocked', $css );

// Restore all asterisks.
		$css = str_replace( '__PRESERVED_ASTERISK__', '*', $css );

// We assume relative and root-relative URLs are safe because they point to resources on the same domain.

// Limit size of CSS to prevent DoS.
		$css = substr( $css, 0, 100000 );

return $css;
	}

/**
	 * Sanitize HTML content allowing a subset of SVG elements.
	 *
	 * @param string $html The HTML to sanitize.
	 *
	 * @return string Sanitized HTML with SVG support.
	 */
	public static function sanitize_html( $html ) {
		$allowed_html = wp_kses_allowed_html( 'post' );

// Selected SVG tags and attributes.
		$svg_tags     = self::wc_kses_safe_svg_tags();
		$allowed_html = array_merge( $allowed_html, $svg_tags );

return wp_kses( self::wc_pre_sanitize_svg( $html ), $allowed_html );
	}

/**
	 * Sanitize SVG content before processing with wp_kses.
	 *
	 * @param string $content The SVG content to sanitize.
	 * @return string Sanitized SVG content.
	 */
	public static function wc_pre_sanitize_svg( $content ) {
		// Remove any xlink:href attributes containing javascript.
		$content = preg_replace( '/xlink:href\s*=\s*(["\'])\s*javascript:.*?\1/i', '', $content );

// Remove foreignObject elements (can contain arbitrary HTML).
		$content = preg_replace( '/<foreignObject\b[^>]*>.*?<\/foreignObject>/is', '', $content );

return $content;
	}

/**
	 * Add limited SVG support to wp_kses_post with XSS protection.
	 *
	 * @return array Array of allowed SVG tags and their attributes.
	 */
	public static function wc_kses_safe_svg_tags() {
		// SVG elements and attributes - security focused.
		return array(
			'svg'            => array(
				'class'               => true,
				'aria-hidden'         => true,
				'aria-labelledby'     => true,
				'role'                => true,
				'xmlns'               => true,
				'width'               => true,
				'height'              => true,
				'viewbox'             => true,
				'viewBox'             => true,
				'preserveAspectRatio' => true,
				'fill'                => true,
				'stroke'              => true,
				'stroke-width'        => true,
				'stroke-linecap'      => true,
				'stroke-linejoin'     => true,
				// Explicitly exclude dangerous attributes.
				'onload'              => false,
				'onclick'             => false,
			),
			'g'              => array(
				'fill'      => true,
				'transform' => true,
				'stroke'    => true,
			),
			'title'          => array(
				'title' => true,
			),
			'path'           => array(
				'd'               => true,
				'fill'            => true,
				'transform'       => true,
				'stroke'          => true,
				'stroke-width'    => true,
				'stroke-linecap'  => true,
				'stroke-linejoin' => true,
			),
			'polyline'       => array(
				'points'       => true,
				'fill'         => true,
				'stroke'       => true,
				'stroke-width' => true,
			),
			'polygon'        => array(
				'points'       => true,
				'fill'         => true,
				'stroke'       => true,
				'stroke-width' => true,
			),
			'circle'         => array(
				'cx'           => true,
				'cy'           => true,
				'r'            => true,
				'fill'         => true,
				'stroke'       => true,
				'stroke-width' => true,
			),
			'rect'           => array(
				'x'            => true,
				'y'            => true,
				'width'        => true,
				'height'       => true,
				'fill'         => true,
				'stroke'       => true,
				'stroke-width' => true,
				'rx'           => true,
				'ry'           => true,
			),
			'line'           => array(
				'x1'           => true,
				'y1'           => true,
				'x2'           => true,
				'y2'           => true,
				'stroke'       => true,
				'stroke-width' => true,
			),
			'defs'           => array(),
			'linearGradient' => array(
				'id'            => true,
				'x1'            => true,
				'y1'            => true,
				'x2'            => true,
				'y2'            => true,
				'gradientUnits' => true,
			),
			'radialGradient' => array(
				'id'            => true,
				'cx'            => true,
				'cy'            => true,
				'r'             => true,
				'gradientUnits' => true,
			),
			'stop'           => array(
				'offset'       => true,
				'stop-color'   => true,
				'stop-opacity' => true,
				// Remove style which can contain JavaScript.
				'style'        => false,
			),
			// Removed potentially risky elements.
			// 'use' - can reference external content.
			// 'mask' - not commonly needed and adds complexity.
		);
	}
}

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