This morning, a friend sent me a link to a story about a vulnerability in Cursor. Anyone who reads my blog or has heard me speak so far in 2025 knows how big of a fan I am of Cursor, which I use to write all my Python code these days.
When I read the article, it was discussing a newly revealed attack technique involving Cursor’s rules files. I’ve talked about rules files before, but for those unfamiliar, they allow you to set up permanent guidelines for Cursor to follow—either for everything or just for specific projects. These are essentially permanent directives like “always try to focus on this” or “always try to avoid that,” which help Cursor align with your coding preferences.
The vulnerability comes into play with shared rules files. Apparently, what this research group discovered was that bad actors could take a rules file and use Unicode to embed text that’s invisible to human eyes but that Cursor would still interpret and execute. This could lead to Cursor essentially inserting backdoors into your code—because that’s exactly what the malicious rules would instruct it to do.
My immediate reaction was relief that I wrote my own rules file from scratch. I borrowed concepts from a few examples I saw in different places, but I created my entire file myself rather than downloading someone else’s.
It’s important to understand what this vulnerability really is. This isn’t unique to Cursor—any programming tool, development IDE, or system that follows a list of automated instructions could be vulnerable if someone can insert malicious text through some method. This is more about the risks of blindly using third-party configurations than about Cursor specifically.
With headlines like this, I get it—people want to raise attention for their work, and it’s absolutely a good thing to be aware of these risks. But this is also a reminder not to “throw the baby out with the bathwater.” Some people are already very slow to adopt AI tools, and they’ll point to issues like this as justification. Yes, it’s a real concern, but the productivity increase you get from tools like Cursor is simply too significant to ignore.
The answer isn’t to abandon these powerful tools—it’s to follow best practices and use them safely. The productivity gains are nothing short of transformative when you do.
So yes, be cautious about where you get your configurations from, but don’t let this scare you away from embracing tools that can dramatically improve your workflow.
