Google has been found to have indexed invitation links for private WhatsApp groups, which makes them discoverable and available for anyone to join, Vice reported on Friday. The Facebook-owned messaging app’s “invite to group via link” feature is meant to allow people to share access to their private groups with others.

Deutsche Welle journalist Jordan Wildon first wrote about the bug. “Your WhatsApp groups may not be as secure as you think they are,” he tweeted. “Point is, any group link that is shared it outside of secure, private messaging can relatively easily be found and joined.”

Vice found private groups using specific Google searches, and most of them included porn-sharing groups. The website also joined a group of non-governmental organisations accredited by the United Nations and got access to all the details of the 48 participants and their phone numbers.

WhatsApp spokesperson Alison Bonny told Vice that invitation links that are posted publicly on the internet can be found by other users of the messaging application. “Links that users wish to share privately with people they know and trust should not be posted on a publicly accessible website,” Bonny added.

Danny Sullivan, Google’s public search liaison, said the company offers tools that allow sites to block content that can be listed in search results. “Search engines like Google and others list pages from the open web,” he tweeted. “That’s what’s happening here. It’s no different than any case where a site allows URLs to be publicly listed.”