wp_validate_redirect( string $location, string $fallback_url = '' ): string

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/**
 * Validates a URL for use in a redirect.
 *
 * Checks whether the $location is using an allowed host, if it has an absolute
 * path. A plugin can therefore set or remove allowed host(s) to or from the
 * list.
 *
 * If the host is not allowed, then the redirect is to $fallback_url supplied.
 *
 * @since 2.8.1
 *
 * @param string $location     The redirect to validate.
 * @param string $fallback_url The value to return if $location is not allowed.
 * @return string Redirect-sanitized URL.
 */
function wp_validate_redirect( $location, $fallback_url = '' ) {
	$location = wp_sanitize_redirect( trim( $location, " \t\n\r\0\x08\x0B" ) );
	// Browsers will assume 'http' is your protocol, and will obey a redirect to a URL starting with '//'.
	if ( str_starts_with( $location, '//' ) ) {
		$location = 'http:' . $location;
	}

	/*
	 * In PHP 5 parse_url() may fail if the URL query part contains 'http://'.
	 * See https://bugs.php.net/bug.php?id=38143
	 */
	$cut  = strpos( $location, '?' );
	$test = $cut ? substr( $location, 0, $cut ) : $location;

	$lp = parse_url( $test );

	// Give up if malformed URL.
	if ( false === $lp ) {
		return $fallback_url;
	}

	// Allow only 'http' and 'https' schemes. No 'data:', etc.
	if ( isset( $lp['scheme'] ) && ! ( 'http' === $lp['scheme'] || 'https' === $lp['scheme'] ) ) {
		return $fallback_url;
	}

	if ( ! isset( $lp['host'] ) && ! empty( $lp['path'] ) && '/' !== $lp['path'][0] ) {
		$path = '';
		if ( ! empty( $_SERVER['REQUEST_URI'] ) ) {
			$path = dirname( parse_url( 'http://placeholder' . $_SERVER['REQUEST_URI'], PHP_URL_PATH ) . '?' );
			$path = wp_normalize_path( $path );
		}
		$location = '/' . ltrim( $path . '/', '/' ) . $location;
	}

	/*
	 * Reject if certain components are set but host is not.
	 * This catches URLs like https:host.com for which parse_url() does not set the host field.
	 */
	if ( ! isset( $lp['host'] ) && ( isset( $lp['scheme'] ) || isset( $lp['user'] ) || isset( $lp['pass'] ) || isset( $lp['port'] ) ) ) {
		return $fallback_url;
	}

	// Reject malformed components parse_url() can return on odd inputs.
	foreach ( array( 'user', 'pass', 'host' ) as $component ) {
		if ( isset( $lp[ $component ] ) && strpbrk( $lp[ $component ], ':/?#@' ) ) {
			return $fallback_url;
		}
	}

	$wpp = parse_url( home_url() );

	/**

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