A developer has demonstrated how to bypass WebUSB restrictions in Firefox by emulating a U2F security key, sparking renewed debate about browser hardware access capabilities. The proof-of-concept shows how a Raspberry Pi Pico can be programmed to communicate with web pages through Firefox despite the browser's lack of WebUSB support, highlighting the complex balance between functionality and security in modern browsers.
The hack works by exploiting the fact that while Firefox doesn't support WebUSB, it does support U2F security keys. By programming a microcontroller to pretend to be a security key and smuggling arbitrary data through the key handle and signature fields of U2F authentication messages, the developer created a backdoor communication channel. This allows websites to control hardware like LEDs on the device without requiring explicit WebUSB support.
The WebUSB Divide: Chrome vs. Firefox and Safari
The comments reveal a deep divide in the tech community regarding WebUSB support. Chrome (and Chromium-based browsers) supports WebUSB, while Firefox and Safari have deliberately chosen not to implement it. This isn't merely a technical difference but reflects fundamental philosophical disagreements about browser security models.
Mozilla and Apple have rejected WebUSB on privacy and security grounds, arguing that USB devices aren't designed to handle potentially malicious interactions and that meaningful user consent is difficult to obtain. Google's approach has been to implement the feature with permission prompts and device blocklists, particularly for security-sensitive devices like FIDO/U2F keys.
WebUSB Support by Major Browsers
- Chrome/Chromium: Fully supported
- Firefox: Not supported (security and privacy concerns)
- Safari: Not supported (security and privacy concerns)
Common WebUSB Use Cases Mentioned
- Flashing firmware to ESP32 and other microcontrollers
- Configuring programmable keyboards
- Updating hardware like Stadia controllers
- Managing label printers
- Supporting specialized hardware like MiniDisc recorders
Security Concerns
- USB devices not designed for adversarial inputs
- Difficulty obtaining meaningful user consent
- Potential for device fingerprinting
- Similarity between WebUSB prompts and security key prompts
- Risk of phishing attacks through permission confusion
Real-World Use Cases vs. Security Concerns
For many developers and hobbyists, WebUSB offers significant practical benefits. It enables browser-based configuration of keyboards, flashing firmware to microcontrollers like ESP32s, and programming devices without installing platform-specific software. Users of these features describe the experience as magic compared to traditional methods requiring native applications.
However, security experts warn about the potential risks of exposing USB devices to websites. USB protocols weren't designed with web security in mind, and many devices lack protection against malicious inputs. There are also concerns about fingerprinting and tracking through USB device identifiers.
Everyone loves the fact the browser is a secure sandbox, letting users run untrusted code. I don't get why people want to poke so many holes in the sandbox.
The Broader Question: What Should Browsers Do?
This debate touches on a fundamental question about the role of web browsers. Should they be minimal document viewers with limited capabilities, or should they evolve into comprehensive application platforms with access to system resources?
Many commenters note that the alternative to WebUSB is often downloading and installing native applications, which typically have even broader system access and fewer security restrictions than browsers. Others point out that the average user has little need for WebUSB functionality, making the additional security risk questionable for the broader population.
The discussion also highlights the challenge of designing permission systems that provide meaningful consent. Many users click through permission prompts without fully understanding the implications, especially when those prompts look similar to legitimate authentication requests.
As browsers continue to evolve, this tension between expanding capabilities and maintaining security will likely remain at the center of web platform development. The creative hack demonstrated in the article shows both the ingenuity of developers and the complex security considerations that browser vendors must navigate.
Reference: Update: Hi HN et al.!