Bitcoin Gold (BTG) was 51% attacked
Bitcoin Gold is a Bitcoin hard-fork that aims to be GPU-mineable by using the Equihash algorithm with parameters (144, 5) also known as "Zhash". The Bitcoin Gold website claims Zhash "uses more memory than an ASIC can muster, but runs fine on many graphics cards". Bitcoin Gold was previously 51% attacked in May 2018 when it was estimated that up to $18 million worth of BTG was double-spent.
Between Thursday and Friday we detected two deep reorgs on BTG, both of which contained double-spends. Their details are listed below. All times are GMT.