[oogali]

Furthermore, the attacker covered their tracks on the initial payload with an innocuous paragraph in the README. ("Nothing to see here!")

    bad-3-corrupt_lzma2.xz has three Streams in it. The first and third
    streams are valid xz Streams. The middle Stream has a correct Stream
    Header, Block Header, Index and Stream Footer. Only the LZMA2 data
    is corrupt. This file should decompress if --single-stream is used.

The strings of `####Hello####` and `####World####` are there so that if you actually follow the instructions in the README, you get a seemingly valid result.

    $ cat tests/files/bad-3-corrupt_lzma2.xz | xz -d --single-stream
    ####Hello####

They're shell comments so it won't interfere with payload execution.

And lastly, they act as a marker that can be used by a later regex to locate the file _without_ referencing it by name directly nor using the actual Hello and World strings.

    $ gl_am_configmake=`grep -aErls "#{4}[[:alnum:]]{5}#{4}$" $srcdir/ 2>/dev/null`
    $ echo $gl_am_configmake
    ./tests/files/bad-3-corrupt_lzma2.xz