convert image from RGB to raw data using ImageMagick convert tool:
`convert image.png RGB:data`

then, we see content is a ZPAQ archive...
`mv data data.zpaq`
`zpaq -x data.zpaq`

and we'll get a hxp-home ext4 drive. Just try to mount it using mount:
`sudo mkdir -p /mnt/hxp`
`sudo mount -t ext4 -o loop, hxp-home /mnt/hxp`

then after by greppiing for flag you'll see some records in .viminfo and .bash_history..we can recover content of file using vim:
`cd /mnt/hxp`
`HOME=$PWD`
`sudo vim -c 'normal @q' -c ':wq! flag.txt'`

then just cat the flag:
`cat flag.txt`

`hxp{piece-of-cake}`