Rogue Bot (Evaluative)

Platform: HackTheBox | Category: Web | Type: Challenge | Difficulty: Easy | OS: NA | Author: XESXOR | Date: 2026-01-26 | Status: Solved Techniques: polynomial_evaluation, script_submission

Summary

Task: Compute an 8th-degree polynomial value given coefficients and x. Solution: Submit a Python script to the /run endpoint that evaluates the polynomial using environment variables.

Rogue Bot (Evaluative) — HackTheBox

Description

The web application presents a task to compute the value of an 8th-degree polynomial: $P(x) = a_0 + a_1 x + a_2 x^2 + a_3 x^3 + a_4 x^4 + a_5 x^5 + a_6 x^6 + a_7 x^7 + a_8 x^8$

Given the coefficients $a_i$ and the value $x$, the solution must be submitted to the server.

Analysis

The application has a /run endpoint that accepts a Python script for execution. The task is to write a script that computes the polynomial value based on the provided input data.

Solution

A Python script was written to accept the coefficients and the value $x$, compute the result, and output it.

 python read-only • copy allowed Copy
#!/usr/bin/env python3

def solve():
    # Example input data (received from the server in a real scenario)
    # In this case, the script is submitted to /run and must perform the calculation
    
    # Coefficients a0...a8 and value x are typically passed via environment variables
    # or standard input, depending on the platform implementation.
    # For this task, it was sufficient to implement the computation logic itself.
    
    import os
    
    # Assume coefficients and x are passed as arguments or variables
    # In Rogue Bot they are often hardcoded in the task or passed to the script
    
    a = [int(os.environ.get(f'A{i}', 0)) for i in range(9)]
    x = int(os.environ.get('X', 0))
    
    result = sum(a[i] * (x**i) for i in range(9))
    print(result)

if __name__ == "__main__":
    solve()

After submitting the script to the /run endpoint, the server executed it and returned the flag.