Et Tu, Grammarly?
Published on: 2025-05-23 05:27:33
Saturday 29 Mar 2025
For a few months now I’ve received sporadic reports that my website was broken. They said the layout was askew and things were sized strangely. They had screenshots to prove it. This was embarrassing for a professional website builder.
Thankfully my audience is tech-savvy and the Grammarly browser extension was identified as a prime suspect. When this extension was installed it broke my website, simple as that. My initial response was: “Sorry, their bug, not mine”. But after one report too many, I was forced to sign-up and install Grammarly myself (praise the burner email).
Discovery
After accepting the Grammarly Firefox (Mullvad browser) extension kitchen sink permissions:
Access your data for all websites
Display notifications to you
Access browser tabs
I soon found the evidence. Grammarly injects a stylesheet into web pages (here’s a GitHub Gist). This stylesheet is loaded from the local extension assets. It cannot be found by the web page itself using S
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