If you're using Electrum or a derivative, you may receive a message like this:


This message is false, sent to you by a hacker. If you click the link in the message and install the software, then your BTC will be stolen. If you ignore the message, then you should be OK. Version 3.3.2, released a week ago, makes the messages less readable/convincing, though you could still receive such messages.

Note that altcoin derivatives of Electrum are very common, with over 1600 forks on github, and they will also be affected.

More info:
https://github.com/spesmilo/electrum/issues/4968

Discussion:
https://bt.irlbtc.com/view/5089963.0