BTC Error Code -26 Txn Mempool.

[sellcoins]

This issue was reported by multiple people back in the 2019, now some other people are reporting It on blockchain.
A guy paid $30 with a 0.08$ Fee, and this error came and then without him even knowing the payment was sent. This is dangerous As fuck. How do we avoid this? (Since i also use blockchain)? Is It because of the low fee?.

[akhjob]

Are you talking about "txn-mempool-conflict" error? If this is the case, the guy would have sent a transaction with too low fees and then tried to re-spend the same bitcoin. Since the fee was too low, the original payment would have gone through at a later period of time, once the mempool was less congested.

How do we avoid this? (Since I also use blockchain)? Is It because of the low fee?.

Since Blockchain.com doesn't support RBF, the only solution is to wait it out until the original transaction gets through. This situation wouldn’t have arisen if he had used a wallet like Electrum which supports RBF or used higher fees.

[nc50lc]

-snip- This is dangerous As fuck. How do we avoid this? (Since i also use blockchain)? Is It because of the low fee?.

You'll get that "-26 error" if there is an input(s) in your transaction that's already spent.

-snip-
A guy paid $30 with a 0.08$ Fee, and this error came and then without him even knowing the payment was sent. This is dangerous As fuck. How do we avoid this? (Since i also use blockchain)?
Is It because of the low fee?.

So that person must be the sender and based from the context, there's another person who's in control of his wallet, private keys or seed phrase.
Like what I've said above, someone has already spent the input(s) that he's trying to spend.
It doesn't look like because of the fee, it's more a spending "race" between that user and the hacker, he broadcast late.

How can you avoid it? Triple your security, start by not using online wallets.
BTW, where's the link to that "report" so I can judge if it's something you should get worked up with?

[sellcoins]

Brother theres no hacker. It happened on another forum i dont think btalk will allow me to name It. I dont think the guy was trying to double spend but all i noticed is that he had a low As fuck fee on a bigger transaction

[khaled0111]

@sellcoins,
There is nothing wrong in copy pasting that post here as long as you add a link to the source.

0,08$ isn't a small fee in fact (depending on the transaction size): it's ~7 sat/byte for a transaction with 1 input and 2 outputs which is more than enough to have it confirmed within few minutes.

[akhjob]

Brother theres no hacker. It happened on another forum i dont think btalk will allow me to name It. I dont think the guy was trying to double spend but all i noticed is that he had a low As fuck fee on a bigger transaction

Unless you explain the situation clearly, nobody can help you here. And as @khaled mentioned 0.08$ fee is not that low of a fee for a standard transaction with lesser number of inputs and outputs. You can literally have 1 sat/byte fee and get the transaction confirmed within 12 hours. Btw, if you are worried whether your fee is very low, you can always check a fee estimator (https://coinb.in/#fees) and adjust the fee accordingly.

[nc50lc]

Brother theres no hacker. -snip-

Then what's the actual issue?
Setting a very low fee won't be a threat unless you're the receiver, paying something that has a deadline or you're in a hurry.

But based from that ambiguous underlined phrase (from my quote), it sounds like he's trying to send BTC but someone already 'sent' the payment without his consent and the error indicated that the inputs were spent.
Try to rephrase that part that will make sense.