Particulars right here: https://github.com/spesmilo/electrum/issues/4968
copy paste from SomberNight within the github problem:
TL;DR: There may be an ongoing assault towards customers the place servers increase exceptions when a consumer broadcasts a transaction; on this case the error textual content is displayed as is within the consumer GUI. The attacker has spawned numerous servers on completely different /16 IPv4s to extend his possibilities of being linked to. The error messages try to get the person to obtain and set up malware (disguised as up to date variations of electrum).`
apparently earlier Electrum variations enable richtext in error messages despatched by the server, so the improve warning would possibly look legit to individuals…
All the time bear in mind to confirm pgp / gpg signatures of bitcoin software program you put in.