CRA is reporting that all of its online services are back in service after being down since Friday afternoon due to an "internet vulnerability" that was discovered during website maintenance.
CRA Website update says
'The Canada Revenue Agency (CRA) is pleased to report that all of its digital services were returned to service on Sunday, March 12 starting at 5:00 p.m. EDT. Individuals, businesses and representatives are now able to file returns, make payments, and access other digital services available through the CRA’s website, including all our secure portals.'