Toilet Leaking; Floor Ruined; Don't See Water: Help!

[plumbing newbee]

Toilet is 50 years old; never had a problem. Over the past year have noticed discoloration around linoleum where toilet sits on the floor; and now the floor is "soft" around that area, indicating a water leak. I have two questions:
First, what is the most likely source of the leak; the floor around the base of the toilet is bone dry.
Second, who do I contact to get this repaired? Will the plumber do the demo and floor repair, ...or do I need a carpenter and a plumber; or will a general contractor do it all...I just don't know how much plumbing contractors do besides the actual plumbing...
Any chance this is covered by my home owner's insurance???
Thanks for the help!

 

[Redwood]

You probably had a leaking wax ring and now the floor is rotted.
You probably will need both a plumber and a carpenter...

 

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[Cookie]

My homeowners covered replacing my floor, the works, and even bringing in restoration services with an air-scrubber, and dehumidifier. I guess it might depend on which company you have but, I didn't have a problem at all. It only didn't cover what it cost to set the toilet back down.