VANCOUVER -- A Vancouver law firm says a class action lawsuit has been launched on behalf of six million Canadians whose personal information was compromised by a data breach at Capital One Financial Corp.

Ted Charney, lead counsel of Charney Lawyers, says the breach may turn out to be "extremely serious."

In addition to credit card application data such as phone numbers, email addresses, dates of birth and self-reported income, the hacker was also able to access credit scores, credit limits and balances, as well as fragments of transaction information from a total of 23 days in 2016, 2017 and 2018.

Charney says the account information is highly sensitive and in the wrong hands could be used to commit identity fraud or to cause damage to credit reputations.

The hacker is alleged to have been in possession of the data since March, but it remains unclear to what extent the hacker sold or distributed the data online.

The Office of the Privacy Commissioner of Canada says it is investigating the hack, which included one million social insurance numbers that had been accessed without authorization.