Source

File: wp-includes/class-wp-simplepie-sanitize-kses.php

public function sanitize( $data, $type, $base = '' ) {
		$data = trim( $data );
		if ( $type & SIMPLEPIE_CONSTRUCT_MAYBE_HTML ) {
			if ( preg_match( '/(&(#(x[0-9a-fA-F]+|[0-9]+)|[a-zA-Z0-9]+)|<\/[A-Za-z][^\x09\x0A\x0B\x0C\x0D\x20\x2F\x3E]*' . SIMPLEPIE_PCRE_HTML_ATTRIBUTE . '>)/', $data ) ) {
				$type |= SIMPLEPIE_CONSTRUCT_HTML;
			} else {
				$type |= SIMPLEPIE_CONSTRUCT_TEXT;
			}
		}
		if ( $type & SIMPLEPIE_CONSTRUCT_BASE64 ) {
			$data = base64_decode( $data );
		}
		if ( $type & ( SIMPLEPIE_CONSTRUCT_HTML | SIMPLEPIE_CONSTRUCT_XHTML ) ) {
			$data = wp_kses_post( $data );
			if ( 'UTF-8' !== $this->output_encoding ) {
				$data = $this->registry->call( 'Misc', 'change_encoding', array( $data, 'UTF-8', $this->output_encoding ) );
			}
			return $data;
		} else {
			return parent::sanitize( $data, $type, $base );
		}
	}