Not very dangerous, at this point in time. Kreps on Security says that only about 100 affected computer users have paid the ransom. Even so, Microsoft has issued this Windows operating system patch. So you might want to update your system.
There is also a software program specifically designed to fight ransomware, called CryptoPrevent. Get the free version here. There’s no guarantee that this program will keep your computer safe from every new ransomware that might be invented, but it’s free and has a good review by the editors at Tom’s Guide.
You might also want to consider using the free version of MalwareBytes, which fights a large array of malicious software programs.