Nextcloud Servers Hit by Sneaky Backdoor Attack

Michael Miller · 2026-10-14

### The Sneaky Backdoor That Caught Admins Off Guard Imagine waking up to find your Nextcloud server has been quietly backdoored. That's exactly what happened to at least three administrators who reported a critical flaw in an optional app called Collabora Online - Built-in CODE Server. The first attack was logged on September 10, and it's a wake-up call for anyone running Nextcloud with this add-on. So, what's the big deal? Attackers exploited a vulnerability to plant web shells on Nextcloud servers. A web shell is a tiny file that lets an attacker run any command they want through a simple web request. And here's the kicker: it runs with the same rights as the web server account. That means full control. ### Why This Flaw Is a Big Deal If you're using Collabora Online's built-in CODE server, you might be at risk. This app is optional, but many admins install it for document editing. The flaw allows attackers to upload a web shell and then execute commands remotely. They can steal data, install malware, or pivot to other systems. It's like leaving a spare key under the doormat for a burglar. Three admins have already reported the issue on GitHub, but who knows how many others are affected? The attacks started on September 10, and there's no official patch yet. That's scary. ### How to Protect Your Nextcloud Server First, don't panic. But do take action. Here's what you can do right now: - **Disable the Collabora Online - Built-in CODE Server app** if you're not using it. It's optional, so you might not need it. - **Check for web shells** by scanning your server for suspicious files. Look for odd names or recently modified files. - **Monitor logs** for unusual activity, especially around September 10. - **Apply updates** as soon as they're available. Keep an eye on Nextcloud's security advisories. Remember, security is a moving target. What works today might not work tomorrow. ### The Bigger Picture: Why Antidetect Browsers Matter You might wonder what this has to do with antidetect browsers. Well, attackers often use these tools to hide their tracks when launching attacks. They can spoof browser fingerprints, manage multiple accounts, and avoid detection. As a security professional, understanding these tools helps you stay one step ahead. If you're managing multiple online identities or doing web scraping, antidetect browsers can be a game-changer. But they're also a double-edged sword. Hackers use them too. > "The best defense is a good offense. Know your tools, and know your enemy." ### Final Thoughts This Nextcloud vulnerability is a reminder that even optional apps can open doors for attackers. Stay vigilant, keep your systems patched, and always monitor for unusual activity. And if you're in the market for an antidetect browser, choose one that's built for security professionals, not just anonymity. Stay safe out there.