Source

File: wp-admin/update-core.php

function dismissed_updates() {
	$dismissed = get_core_updates(
		array(
			'dismissed' => true,
			'available' => false,
		)
	);
	if ( $dismissed ) {

		$show_text = esc_js( __( 'Show hidden updates' ) );
		$hide_text = esc_js( __( 'Hide hidden updates' ) );
		?>
	<script type="text/javascript">
		jQuery(function( $ ) {
			$( 'dismissed-updates' ).show();
			$( '#show-dismissed' ).toggle( function() { $( this ).text( '<?php echo $hide_text; ?>' ).attr( 'aria-expanded', 'true' ); }, function() { $( this ).text( '<?php echo $show_text; ?>' ).attr( 'aria-expanded', 'false' ); } );
			$( '#show-dismissed' ).click( function() { $( '#dismissed-updates' ).toggle( 'fast' ); } );
		});
	</script>
		<?php
		echo '<p class="hide-if-no-js"><button type="button" class="button" id="show-dismissed" aria-expanded="false">' . __( 'Show hidden updates' ) . '</button></p>';
		echo '<ul id="dismissed-updates" class="core-updates dismissed">';
		foreach ( (array) $dismissed as $update ) {
			echo '<li>';
			list_core_update( $update );
			echo '</li>';
		}
		echo '</ul>';
	}
}