Source

File: wp-includes/bookmark.php

function sanitize_bookmark_field( $field, $value, $bookmark_id, $context ) {
	switch ( $field ) {
		case 'link_id': // ints
		case 'link_rating':
			$value = (int) $value;
			break;
		case 'link_category': // array( ints )
			$value = array_map( 'absint', (array) $value );
			// We return here so that the categories aren't filtered.
			// The 'link_category' filter is for the name of a link category, not an array of a link's link categories.
			return $value;

		case 'link_visible': // bool stored as Y|N
			$value = preg_replace( '/[^YNyn]/', '', $value );
			break;
		case 'link_target': // "enum"
			$targets = array( '_top', '_blank' );
			if ( ! in_array( $value, $targets, true ) ) {
				$value = '';
			}
			break;
	}

	if ( 'raw' === $context ) {
		return $value;
	}

	if ( 'edit' === $context ) {
		/** This filter is documented in wp-includes/post.php */
		$value = apply_filters( "edit_{$field}", $value, $bookmark_id );

		if ( 'link_notes' === $field ) {
			$value = esc_html( $value ); // textarea_escaped
		} else {
			$value = esc_attr( $value );
		}
	} elseif ( 'db' === $context ) {
		/** This filter is documented in wp-includes/post.php */
		$value = apply_filters( "pre_{$field}", $value );
	} else {
		/** This filter is documented in wp-includes/post.php */
		$value = apply_filters( "{$field}", $value, $bookmark_id, $context );

		if ( 'attribute' === $context ) {
			$value = esc_attr( $value );
		} elseif ( 'js' === $context ) {
			$value = esc_js( $value );
		}
	}

	return $value;
}