wp_ajax_send_attachment_to_editor

function wp_ajax_send_attachment_to_editor() {
	check_ajax_referer( 'media-send-to-editor', 'nonce' );

	$attachment = wp_unslash( $_POST['attachment'] );

	$id = intval( $attachment['id'] );

	$post = get_post( $id );
	if ( ! $post ) {
		wp_send_json_error();
	}

	if ( 'attachment' !== $post->post_type ) {
		wp_send_json_error();
	}

	if ( current_user_can( 'edit_post', $id ) ) {
		// If this attachment is unattached, attach it. Primarily a back compat thing.
		$insert_into_post_id = intval( $_POST['post_id'] );

		if ( 0 == $post->post_parent && $insert_into_post_id ) {
			wp_update_post(
				array(
					'ID'          => $id,
					'post_parent' => $insert_into_post_id,
				)
			);
		}
	}

	$url = empty( $attachment['url'] ) ? '' : $attachment['url'];
	$rel = ( strpos( $url, 'attachment_id' ) || get_attachment_link( $id ) == $url );

	remove_filter( 'media_send_to_editor', 'image_media_send_to_editor' );

	if ( 'image' === substr( $post->post_mime_type, 0, 5 ) ) {
		$align = isset( $attachment['align'] ) ? $attachment['align'] : 'none';
		$size  = isset( $attachment['image-size'] ) ? $attachment['image-size'] : 'medium';
		$alt   = isset( $attachment['image_alt'] ) ? $attachment['image_alt'] : '';

		// No whitespace-only captions.
		$caption = isset( $attachment['post_excerpt'] ) ? $attachment['post_excerpt'] : '';
		if ( '' === trim( $caption ) ) {
			$caption = '';
		}

		$title = ''; // We no longer insert title tags into <img> tags, as they are redundant.
		$html  = get_image_send_to_editor( $id, $caption, $title, $align, $url, $rel, $size, $alt );
	} elseif ( wp_attachment_is( 'video', $post ) || wp_attachment_is( 'audio', $post ) ) {
		$html = stripslashes_deep( $_POST['html'] );
	} else {
		$html = isset( $attachment['post_title'] ) ? $attachment['post_title'] : '';
		$rel  = $rel ? ' rel="attachment wp-att-' . $id . '"' : ''; // Hard-coded string, $id is already sanitized.

		if ( ! empty( $url ) ) {
			$html = '<a href="' . esc_url( $url ) . '"' . $rel . '>' . $html . '</a>';
		}
	}

	/** This filter is documented in wp-admin/includes/media.php */
	$html = apply_filters( 'media_send_to_editor', $html, $id, $attachment );

	wp_send_json_success( $html );
}