In Florida, the owner of a dog that bites / attacks another is liable for that person’s injuries, regardless of if the dog had shown viciousness in the past.

Florida Statute 767.04. Dog owner’s liability for damages to persons bitten;

The owner of any dog that bites any person while such person is on or in a public place, or lawfully on or in a private place, including the property of the owner of the dog, is liable for damages suffered by persons bitten, regardless of the former viciousness of the dog or the owners’ knowledge of such viciousness. However, any negligence on the part of the person bitten that is a proximate cause of the biting incident reduces the liability of the owner of the dog by the percentage that the bitten person’s negligence contributed to the biting incident. 

A person is lawfully upon private property of such owner within the meaning of this act when the person is on such property in the performance of any duty imposed upon him or her by the laws of this state or by the laws or postal regulations of the United States, or when the person is on such property upon invitation, expressed or implied, of the owner. However, the owner is not liable, except as to a person under the age of 6, or unless the damages are proximately caused by a negligent act or omission of the owner, if at the time of any such injury the owner had displayed in a prominent place on his or her premises a sign easily readable including the words “Bad Dog.” The remedy provided by this section is in addition to and cumulative with any other remedy provided by statute or common law.