TORONTO - Two Canadian law firms say they have filed a $578 million class-action lawsuit against the companies that run Ashley Madison after a hacker group's data breach exposed some 39 million memberships in the adultery website earlier this week.

Charney Lawyers and Sutts, Strosberg LLP, both of Ontario, said in a statement that they have filed on behalf of Canadians who subscribed to Ashley Madison and whose personal information was disclosed to the public.

The action is brought against Avid Dating Life Inc. and Avid Life Media Inc., the Toronto-based companies that run AshleyMadison.com.

The plaintiff in the lawsuit is Eliot Shore, an Ottawa widower. Shore says he joined the website for a short time in search of companionship after he lost his wife to breast cancer.