Last week, Canada Revenue Agency suspended efiling for taxpayers as a result of a major security flaw – and now, CRA reveals that it has suffered a breach related to the issue.

On Monday, the agency's commissioner, Andrew Treusch, announced in a statement that the “Heartbleed bug” – a critical OpenSSL flaw affecting many online services and websites – was exploited by an intruder that accessed the social insurance numbers (SINs) of approximately 900 taxpayers.

Treusch said that the breach occurred over a six-hour period, and that he notified the Canada's Privacy Commissioner of the incident on Friday. In the aftermath of the breach, CRA has begun sending notification letters to impacted individuals and has set up a toll-free number for those with further inquiries.