There was a vulnerability in Bitcoin’s code. Meanwhile, since Litecoin and Bitcoin Cash and some others are based on Bitcoin, they also had the bug. Luckily, the Bitcoin Cash developer who caught the code shared it, and Bitcoin, Litecoin, Bitcoin Cash, and more have all fixed the issue. Other crypto teams who based their code on Bitcoin, like Doge and Verge, have come out to assure people that they never had the vulnerability.
In other words, by the time you are hearing the news, the problem has already been fixed by the top developers of the top coins.
The bug would have allowed a malicious actor to inflate the supply of any crypto with the bug.
This 600 microsecond optimization now resulted in CVE-2018–17144. Certainly the most catastrophic bug in recent years, and certainly one of the most catastrophic bugs in Bitcoin ever.
This bug was initially suspected to potentially cause inflation, was reported because it led to reliable crashes and confirmed by closer analysis… to be actually allowing inflation!
The reality is, although any damage could have been undone with forks (for example a fork to rollback the blockchain to before the bug), a widespread exploit that hit coins like Bitcoin, Litecoin, and Bitcoin Cash would have likely caused an epic amount of temporary chaos in the crypto space.
Thus, good news is, not only is the bug fixed, but to the best of anyone’s knowledge the bug was never exploited.
The other good news is, it was a Bitcoin Cash Developer who came along and saved the day here. That is pretty cool since Bitcoin Cash developers are sometimes looked down on by Bitcoin developers (and the two camps are generally warring). Of course, as an investor, you want all the top coins to play nice and not do the old PC vs. Apple thing. So in this sense it is nice for the big dogs to owe credit to the underdogs. Anyway, that is all really an aside.
Back to the bug, there is some bad news.
The bad news is Bitcoin is the model for many cryptos, and while most top projects were competent enough to fix the issue ASAP, there is a chance that some smaller coins down the list who don’t take as much care with their coins and code could be at risk. For example, there were about 20 Bitcoin forks in the past 12 months that all copy and pasted Bitcoin’s code.
In short, if you use a coin that uses Bitcoin’s code, and especially if it is down the list in terms of market cap, check their Github and Twitter and make sure they have patched the bug.
NOTE: If you have any coin in the top 100 or so by market cap, you can be dang sure the developers have fixed the bug and probably even addressed the issue to let you know if it was present.