What are you hiding

One night, five very close friends break into their high school. They come to the basement while investigating the school. They made cautious to secure the basement door with a doorstop so they wouldn't be trapped. They muck around for a while but can't seem to find anything to do, so they depart. However, as they leave, they find the door is shut. They've been confined in the basement for a while now. With no access to the internet or a phone signal. They're basically doomed if they accept the fact that they'll be confined in there all night... They decide to go on a short adventure. A chalkboard was discovered by one of them. Those who have the ability to turn over... They all looked at each other in surprise. On the chalk's surface, All of their names were scribbled across it. "EACH OF YOU IS HIDING SOMETHING FROM EACH OTHER," it wrote beside their names. They then begin to panic. However, it was written at the bottom, "IF ANY IF YOU FAIL TO TELL YOUR TRUTH BY MORNING... YOUR SECRET WILL BE UPLOADED TO YOUR SOCIAL MEDIA ACCOUNTS."