Solution

1. Get all the values of the data.data fields [data]

2. Leave only those that cannot be converted to ascii text [nonascii_bytes]

3. Leave only unique lines, keeping the order [unique_nonascii_bytes]

4. Remove values that are the beginning or end of adjacent [definitely_unique_nonascii_bytes]

5. Remove the first value [jpg_bytes] and write to flag.jpg

Flag is here

Original writeup (https://github.com/wetox-team/writeup/tree/master/cybrics_2020/gcloud).