Facebook metric woes continue as it admits under valuing Instant Articles viewers

Facebook has for the fourth time in recent months owned up to providing marketers with inaccurate data, this time revealing it has been underreporting iPhone traffic on some Instant Articles. 
In a blog post published yesterday (16 December) Facebook said that its metrics partner comScore alerted the social giant to the issue, which it said has now been fixed, and has informed the affected publishers. It did not specify which publishers were affected. 
"ComScore alerted us to the