Update: Disney declined to address this specific threat but did release the following statement:
Unfortunately we’ve all been living in a world of uncertainty, and we have been increasing our security measures across our properties for some time, adding such visible safeguards as magnetometers, additional canine units, and law enforcement officers on site, as well as less visible systems that employ state-of-the-art security technologies.
According to People.com, Omar Mateen, the murderer in the Orlando Pulse nightclub mass shooting, visited Walt Disney World in April and, according to his wife, scouted Downtown Disney / Disney Springs as a potential target.