Today we pushed out a Werkzeug bugfix release which contains a security relevant fix. It has come to our attention (reported by Jordan Milne) that the PIN brute-force protection in the Werkzeug debugger could be bypassed by attacking the cookie rather than the PIN. While this is generally not easily fixable we improved the situation by mixing in higher quality secret data into the cookie name and made it more complex. We now include a UUID of the machine the code is running on.
This should make it significantly more complex to bypass the PIN check. That said we want to reiterate that the PIN protection for the debugger is not a suitable protection to run the debugger in production. It's a basic security feature to make it less likely to use an accidentally enabled debugger. Please ensure that you never enable the debugger in production environments regardless of this feature.