Comment by vsskanth

The firmware situation is mixed. The ECU hardware is a standard TAG700 from McLaren. Basically these are software-defined ECUs where you can do whatever. However, FIA has some rules on what you're allowed to modify and has some "compulsory" software in there for monitoring and competition regulatory reasons. It appears there was very limited testing of this module in wet conditions which seems to have affected a lot of vehicles. (I work in Motorsports)