...This in a post on their official website.
The warning goes out because of the potential split happening.
At Tue Aug 01 2017 02:00:00 GMT+0200 (Western Europe, summer time), Bitcoin confirmation scores may become unreliable for an unknown length of time. This means that any bitcoins you receive after that time may later disappear from your wallet or be a type of bitcoin that other people will not accept as payment.
- Bitcoin.org.
Note that the above time is local time for me (Sweden) might be different for you!
Read more @ https://bitcoin.org/en/alert/2017-07-12-potential-split
