Electrum Fee-Bump Bug: How a User Lost 0.87 BTC, and What to Do Now | The Coin Shack

A wallet bug cost one Bitcoiner 0.87 BTC. Here is what to do so it never happens to you.

On October 28, 2026, a long-time Bitcoin owner lost about 0.87 BTC (roughly US$70,000) while moving it to his own safe wallet. He shared the full story on Reddit and YouTube to warn others. Here it is in plain English, with the exact steps to protect yourself.

TL;DR

Update Electrum to version 4.8.3 or newer (Help → About shows your version).
Check the whole address, not just the first and last few letters, every time you approve a payment.
Stuck payment? Don't rush. Look it up on mempool.space before you change anything.
Big amount? Send it in parts and use a hardware wallet.

What happened

He used Electrum, a popular Bitcoin wallet on his computer. Electrum doesn't check the Bitcoin network by itself: it asks a computer on the internet, called a server, what is going on. One of those servers was run by a thief.

He was careful: he sent small test amounts first and checked the address. But when he sent the big amount, it never seemed to go through. The wallet said the fee was too low (the fee is the small tip that gets a payment processed).

So he clicked "Bump fee" to pay a bigger tip. That button re-approved a copy of the payment that the thief's server had quietly changed. The new copy paid an address that only looked like his:

His address: bc1qnjtc6q…mku6537

Where the money went: bc1qzla0gk…tu6537

The start and the last four characters match. Everything in the middle is different. Bitcoin payments can't be reversed, so the money was gone.

Is it fixed?

Yes. Electrum fixed the bug in version 4.8.3, released a few days before this happened. He had downloaded his copy just before the fix came out. If you use Electrum, update today.

Do this today (5 minutes)

Check your version: open Electrum → Help → About. If it says lower than 4.8.3, download the new one, only from electrum.org.
Choose your server yourself: Tools → Network → turn off "Select server automatically" and pick a well-known one.
Avoid stuck payments: Tools → Preferences → Fees → choose "Mempool". This suggests a fee that actually gets your payment through.
Bookmark your safe-wallet address on mempool.space. It is a free public website that shows what really arrives, no matter what your wallet says.

Every time you send: check the address

Check the whole address, 4 characters at a time. Thieves make fake addresses that match the start and end, because that's all most people look at.
Check again on every "Bump fee", "Retry" or "Speed up". Each one is a brand-new approval.
Using a hardware wallet (a small device like Ledger, Trezor or Coldcard)? Read the address on its screen before you press approve. It shows the truth even if your computer is fooled.
Copy and paste addresses, then check after pasting. Some viruses swap copied addresses.

Payment looks stuck? Do this, in order

Stop. Don't click "Bump fee" yet. Nothing is lost while a payment is waiting.
Look it up: copy the payment's ID (the long "Transaction ID") and paste it into mempool.space.
Not found there? Your wallet may be getting fake information. Change server (Tools → Network) and restart Electrum.
Found there? Check that the address it's going to is yours, every character.
Only then bump the fee, and check the address one more time before you approve.

Sending a large amount? Also do this

Send it in parts. Send some, check it arrived on mempool.space, then send the rest.
Don't do it in a hurry. Most mistakes happen when a screen tells you something is urgent.
Ask us to sit with you. Our team in Markham will check your setup and walk you through it, free. For larger savings, our OTC Desk helps set up hardware wallets, and our guide to self-custody for larger holdings explains the options.

Questions

Was this a problem with Bitcoin itself?

No. Bitcoin worked normally. The problem was in one version of one wallet app, which trusted a dishonest server.

I use Electrum. What should I do right now?

Open Help → About. If your version is lower than 4.8.3, update from electrum.org. Then check the full address before every approval, including fee bumps.

Does this affect Bitcoin I buy from The Coin Shack?

No. We send to the address you give us, and you can see it arrive on mempool.space. Keeping it safe afterwards is up to your wallet, so follow the steps above.

Can the lost Bitcoin be recovered?

Unfortunately not. Bitcoin payments can't be reversed, which is why checking before you approve matters so much.