Senate Judiciary Chairman Chuck Grassley, R-Iowa, is pressing Google for answers on what future actions will be taken to safeguard personal information from its users, after Google failed to disclose this year that app developers could access private data from thousands of Google Plus users.

“I write with regard to recent troubling reports that Google exposed the private data of approximately 500,000 Google+ users and then failed to disclose the glitch, despite knowing about it since March,” Grassley wrote to Google CEO Sundar Pichai on Friday.