+Basically, how this exploit works is not much different to the prior exploit, and the PoC is simply a modified version of it. The file uploaded (this time using a .pht file extension, because blacklisting sucks), exists on disc for a mere split second before it fails the image validity check and unlink() is called on it. So we must "beat the unlink call" and request our backdoor file before it gets deleted. The most effective way of doing this is to repeatedly upload the file in one thread, while requesting it in another. The PoC I have written here does this in a rather crude manner, landing us with a shell within about seven to ten seconds.
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