Facebook sent physical mail invitations to the media on Friday to announce a 20 June event.

ABC News first received the snail-mail invite coupled with a letter that claimed a small team has been working on a "big idea". Facebook specifically wrote it would like to discuss a new product at its event.

Read: Facebook potentially launching its own take on Google Reader

A rumor circulated earlier today that claimed Facebook would soon launch its own version of Google Reader. A developer allegedly noticed mentions of RSS feeds in Facebook's code, hinting at the possibility of a reader launch.

Speculation aside, Facebook officially announced this week that it is launching clickable hashtags. The feature enables users to search for and group discussions about a topic - similar to currently existing functions found in Twitter, Instagram, Tumble and Pinterest.

Read: Facebook to implement Twitter-style clickable hashtags

Whether Facebook plans to unveil additional social features or even launch an RSS product, the mystery will certainly unfold at its Menlo Park headquarters in California next week.