doubt a backdoor. too much variablity in manufacturers with propietary software.
they used to think bluray encription was unbreakable too, until one guy found the one spot where it could be read and decoded. that's probably more of what it is here. being able to query the computer and get the signal from it. just bad encryption which underestimated the hackers capablities.
or a particular frequency which confuses them.
i foresee alot of recalls in the near future to deal with this problem.
i'm assuming this is all new vehicles that no longer have a physical key to start them.
(how long til we return to locking steering columns and keys?)