OHK , I completely mis predicted the question and my solution is completely unintended and thats the reason i am sharing it.

So we were given a Docker file and a XML file which we have to tweak and pass into the service to get flag.
So if we pass XML then it must be parsing XML and i tried XML injection(XXE) which eventually worked. So this my XML file

`solution.xml`
```
]> <change-log> <text>&systemEntity;</text> </change-log>
```

And it worked like a rockstar.

Damn I am soo noob to solve it the intended way :(