U2 — Risk cards on browser extensions

Not a proposal to build an extension. It is the estate's security analysis of extensions as a category, and this site needs it as its counterweight: a guidance site teaching people to build extensions that never publishes why extensions are dangerous is selling something.

The read-content closure

The core finding: accepting that an extension can read the content of pages you visit — "which many extensions genuinely need" — quietly means it "can read and act on your behalf on every site you are logged into," so if you are in the AWS console it can do what you can do there, and the same for your email, Salesforce, and the rest. And "even without capturing secrets, injecting scripts and reading content is enough for serious compromise."

The escalation that makes it current

"The risk compounds the moment an agent, even a local one, is connected to the extension, because prompt injection from the very web content the extension reads turns a safe extension into an actor taking instructions from attacker-controlled pages."

The honest frame for this whole site

The recorder's four invariants — never originates, never alters, never throws, never transmits — are not fastidiousness. They are the mitigation for the closure this brief describes. See the ethics position for how the site states this before the code.