Player2 was a challenging but very fun box by MrR3boot and b14ckh34rt. The highlight of the box for me is the finale 2.29 heap pwn! In my opinion, if there were no unintended routes, this would have been by far the hardest box so far, but some of these alternative solutions were never patched.
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The box was rated as insane and required us to grab a client and information from an anonymous FTP server, modify the Java client to exploit lacking server side validation, exploit Java deserialization, and exploit and careless administrator who periodically pulls log archives from within docker containers and extracts them. All in all this box was quite entertaining but not necessarily insane. Rather it mostly was just time-consuming.