# I almost leaked a customer's data while screen-sharing ChatGPT — here's what I built to stop it

> Source: <https://dev.to/mikhailborodin/i-almost-leaked-a-customers-data-while-screen-sharing-chatgpt-heres-what-i-built-to-stop-it-4kn4>
> Published: 2026-06-04 18:38:17+00:00

A few weeks ago I was on a call sharing my screen, walking a teammate through a prompt I'd been iterating on in ChatGPT. Mid-sentence I scrolled up — and there, three messages back, was a chunk of a customer's data I'd pasted in earlier to debug something. Real email, real account info, sitting right there on a shared screen.

Nobody said anything. Maybe nobody noticed. But I noticed, and I spent the rest of the call only half-present, trying to remember everything else still in that thread.

If you live in ChatGPT all day, you already know the problem. The thread *is* your scratchpad. You paste logs, keys, customer rows, half-finished internal docs — things you'd never put in a doc you planned to share. And then someone says "can you share your screen real quick" and suddenly your scratchpad is a presentation.

The standard answers are all some version of "be careful":

These fail for the same reason all manual checklists fail under pressure: the moment you actually need them is the moment you're distracted, talking, and not thinking about hygiene. You remember *after*. The fix has to happen **before** the screen goes live, and it has to require zero discipline in the moment.

I wanted something that just sat there and blurred sensitive parts of a page automatically, so that even if I forgot, the leak couldn't happen. A few requirements:

The naive approach is to listen for some "I'm sharing now" signal and react. That's too late — there's a visible frame where the data is exposed before the blur kicks in. You're racing the screen capture.

The approach that actually works is to apply the blur as a CSS layer that's *already present* on matched elements, and only reveal on explicit interaction (hover-to-peek, or a toggle). Roughly:

```
.privacy-blur {
  filter: blur(8px);
  transition: filter 0.12s ease;
  user-select: none;
}

.privacy-blur:hover {
  filter: blur(0);
}
```

The hard part isn't the blur — it's *deciding what to blur* on an arbitrary page you don't control. You can't hardcode selectors for every site. So you end up with a mix of:

`MutationObserver`

to catch content injected after load — critical for chat apps like ChatGPT, where messages stream in dynamically and a one-time pass on load misses everything.The `MutationObserver`

part was the one I underestimated. In a normal page you blur once on load and you're done. In a streaming chat UI, content arrives continuously, so the observer has to re-run matching on every batch of new nodes — while staying cheap enough not to lag the page. Debouncing the observer callback and only scanning added nodes (not re-scanning the whole DOM) was what made it usable.

I ended up turning it into a small Chrome extension so I'd stop relying on my own memory. It's local-only, blurs matched content before it's visible, and lets you peek per-element. If the same problem bites you, it's [Screen Privacy Blur](https://chromewebstore.google.com/detail/screen-privacy-blur/pfngjkakgncabcfjdknjacpnbidjlldm?utm_source=devto&utm_medium=article&utm_campaign=chatgpt_privacy) on the Chrome Web Store.

But honestly, the extension is secondary to the point I actually want to land:

**Treat your ChatGPT thread like a shared screen by default**, not like a private notebook. The moment you paste anything real into it, assume it could end up in front of someone. Build the habit — or build the guardrail — *before* the "can you share your screen" moment, because that moment never comes with enough warning.

How do you handle this? Separate accounts, a scrub-before-share ritual, something else? Genuinely curious what's worked for people who demo in ChatGPT a lot.