The EXP26 ZX Spectrum core update has been out already for a few weeks:
Be aware you must upgrade BIOS and ZX Spectrum main core at the same time. Just follow the instructions in the readme.
The new 0.73 BIOS will break keyboard support with older ZX Spectrum Cores (T24, EXP25). Therefore the ZX WIFI core will not work properly after the BIOS being updated. Its very likely the ZX WIFI core will eventually be updated to EXP26.