Quote from: Xynerise on February 21, 2019, 07:47:44 PM

The transaction that sent out your bitcoin was made barely seconds after it was received, so most likely there was a script running (probably on your PC) that sent the bitcoin to the attacker's address almost immediately, and also overpaying in fees (88.7sats/byte while the average on that day was ~15 sats per byte).

Like the posters above have said, either your version of electrum is malware, or your computer has been compromised.
Run a complete antivirus scan to find out.

Yup, this is the common flag that suggests a script just lurking and waiting. 88 sats/byte does seem to be the lowest overestimate I've seen from this type of hack. Usually way into high hundreds just to ensure it gets confirmed in next block.

Something is compromised, device, if not the seed/private key itself. Sweep device. Generate new wallet.