I think (and I am definitely no expert), that this is the American Toad (Anaxyrus americanus). It is unlikely to be a Fowler's Toad (Anaxyrus fowleri) or a Woodhouse's Toad (Anaxyrus woodhousii), or a hybrid between Woodhouse's and the American, as I will explain.
Frogs are generally considered to have smooth skin, which this doesn't have; it clearly has bumpy skin, so it is a toad. Note that this isn't a characteristic used by biologists, just an informal characterization used in general parlance.
According to Ontario Nature, the only two species of toad that are found in Ontario are the American Toad and the Fowler's Toad, so it shouldn't be a Woodhouse's Toad, as it isn't found in the province. If you use the map of distributions found here, you will see that the Fowler's toad is rare and only found in southern-most Ontario, near Lake Erie, while the American Toad is found throughout the stateprovince. Also on their page the description of the American toad, the distinguishing characteristic of the American toad from the Fowler's toad is the number of bumps/"warts" on the dark dots on its back.
From the Characteristics section:
The American toad is a large, squat toad with brown, reddish or olive skin and dark blotches containing one to two spots or “warts” of various colours. The belly is white with dark spots. These toads often have a light line down the middle of the back.
From the Similar Species section:
In extreme southern Ontario, the range of the American toad overlaps that of the Fowler’s toad. The best way to distinguish these two toads is by counting how many bumps are in each large dark blotch on the back. Fowler’s toads have three or four bumps per blotch, whereas American toads have one or two.
In your image you can clearly see one bump per dark spot on the back of the toad, as well as a lighter line down the back. The Ontario Nature photos (particularly the ones next to the Similar Species (reproduced below) and Threats and Trends sections ) clearly show a similar pattern of spots to the ones in your photo, whereas the ones for the Fowler's Toad show the smaller, higher number of bumps per spot.
Image copyright: Jason King, reproduced from Ontario Nature https://ontarionature.org/programs/community-science/reptile-amphibian-atlas/american-toad/
These toad species both produce a toxin from their skin, which does affect dogs (and presumably other species), but is apparently only enough to cause the dog to drop the toad; from the Ontario Nature site:
Both tadpoles and toads have poison glands in the skin that reduce their susceptibility to predators. A dog that picks up a toad will drop it and may foam at the mouth but will not be hurt.
