VTP is VLAN Trunking Protocol which propagates VLAN numbers throughout a network. When a switch acting as VTP server with a higher revision number of the VTP database is inserted into the network it can “bomb” the network.
The higher VTP database number will cause VLAN information to be overwritten in all switches. Because the version of the latest database is usually from a switch in the lab which is nothing like the live network, your entire network effectively “dies”.
This is known as a “VTP Bomb”, especially is performed maliciously.