(Wired) Since the WannaCry ransomware ripped through the internet late last week, infecting hundreds of thousands of machines and locking up critical systems from health care to transportation, cryptographers have searched for a cure. Finding a flaw in WannaCry’s encryption scheme, after all, could decrypt all those systems without any ransom.

Now one French researcher says he’s found at least a hint of a very limited remedy. The fix still seems too buggy, and far from the panacea WannaCry victims have hoped for. But if Adrien Guinet’s claims hold up, his tool could unlock some infected computers running Windows XP, the aging, largely unsupported version of Microsoft’s operating system, which analysts believe accounts for some portion of the WannaCry plague.

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