total miners 30328

someone with only 4 bytes in tx_extra mined two blocks in a row and leaved me with orphan block

which blocks cohcho ?

I don't know such pools and it's not monerod

2025528, 2025529

yeah, doesn't seem to be from a large well known pool

I've received their block within 500ms after monerod had broadcasted my own and then got reorg. And both blocks have 39 bytes long tx_extra or 4 bytes long extra_nonce. Therefore i'm sure they mined both blocks

is there any real defense against selfish mining?

but that does suggest that the miner has significant hash power

have they mined any other blocks with that signature?