Hi - Thanks for the report. I see that other sites are showing the 27.33 low as well for 24 Aug 2015. It certainly doesn't appear to be correct. I will send this to our engineering team for investigation.
The 24-Aug-2015 low for BATS:CSM of $27.33 is likely correct. That was the day of a sharp market decline of nearly 1,000 points (intraday) on the Dow. Most other sites show the same OHLC prices as YF.
It's difficult to know for sure what the intraday low was for that day more than 2 years ago.
Great info! That sounds like it may be the issue since the other sources I checked showed the same data we have. I'll send your info to the engineering team assigned this case. Thank you.