"The hack is quite simple. The Linux system running on the scope has a default root password of, you guessed it, “root”." 
https://twitter.com/hackaday/status/1075496258159108096 …
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Or maybe they don't really care -- they figure 99% of owners aren't going to try it, so why bother?
According to some eevblog forum posts it looks like this is simply the default root password from the Xilinx reference linux rootfs for the zynq. (The MD5 password hash is using the same seed value in both cases.)