Microsoft is working on a fix for what browser maker Vivaldi and a Google researcher say are major performance issues caused to Chromium.

Microsoft aknowledged the issues caused by updates released to Windows 10’s built-in Control Flow Guard (CFG) security feature. The Wimndows update can cause massive performance issues for Google Chromium-based browsers (such as Chrome, Microsoft’s Edge browser, Vivaldi and many others). The problem was first identified by Vivaldi then replicated by Google.

Tests on impacted Windows 10 PCs found Chromium performance runs 3-4x slower on average than on Windows 7, which is not affected by the issue.

"We immediately noticed performance problems. A test suite that previously took about 100 minutes to run, now took 300 or even 360 minutes," wrote Vivaldi developer Yngve Pettersen. "[It’s a] huge Windows 10 performance issue to Chromium… One of the tests that took 100 minutes when run on Windows 10 on this machine, took 20 minutes on Windows 7.”

The fix Chromium programmer Bruce Dawson discovered was to turn off CFG, after which some tests were running between five and 20 times faster while one browser process ran 200 times faster.