The Beast

The Beast is a new hostile mob that was added in V4.82.

Encounters

The Beast occurs either naturally in the wild or as a consequence of a player's actions. If a wolf happens upon and eats or is intentionally fed rotted flesh (drops from Zombies)then it will transform from a normal wolf to a Beast. In either case the results are the same. As a side effect of that transformation, it will take on a skin texture similar to that of a hostile wolf and become hostile to any player that happens to be nearby. Upon its death, the beast will not drop wolf chops like a normal mob but, will drop more rotted flesh. It will also no longer produce dung.

Combat

Fighting off a beast is a simple matter. A pack of beasts, however, can be an issue and should be handled very much like if you managed to aggro a regular pack of wolves: run, unless you're armed and armored reasonably well. Beasts that attempt to harm you will do so only from melee range. They have the added drawback of being able to bump the player and cause movement in the process, which can lead to unintended fall damage. Like other hostile mobs, if you are being accompanied by your own pack of wolves, your pups will attempt to attack the beast/s.

Video Evidence

There is no evidence. Experience by yourself.