Source

File: wp-includes/blocks.php

function filter_block_kses( $block, $allowed_html, $allowed_protocols = array() ) {
	$block['attrs'] = filter_block_kses_value( $block['attrs'], $allowed_html, $allowed_protocols );

	if ( is_array( $block['innerBlocks'] ) ) {
		foreach ( $block['innerBlocks'] as $i => $inner_block ) {
			$block['innerBlocks'][ $i ] = filter_block_kses( $inner_block, $allowed_html, $allowed_protocols );
		}
	}

	return $block;
}