File Browser is a file managing interface for uploading, deleting, previewing, renaming, and editing files within a specified directory. Prior to 2.63.1, the fix in commit b6a4fb1 ("self-registered users don't get execute perms") stripped Execute permission and Commands from users created via the signup handler. The same fix was not applied to the proxy auth handler. Users auto-created on first successful proxy-auth login are granted execution capabilities from global defaults, even though the signup path was explicitly changed to prevent execution rights from being inherited by automatically provisioned accounts. This vulnerability is fixed in 2.63.1.

Affected: Go: github.com/filebrowser/filebrowser/v2

## Summary

The fix in commit `b6a4fb1` ("self-registered users don't get execute perms") stripped `Execute` permission and `Commands` from users created via the signup handler. The same fix was not applied to the proxy auth handler. Users auto-created on first successful proxy-auth login are granted execution capabilities from global defaults, even though the signup path was explicitly changed to prevent execution rights from being inherited by automatically provisioned accounts.

Confirmed on v2.62.2 (commit 860c19d).

## Root Cause

`auth/proxy.go` `createUser()` applies defaults without restriction:

user := &users.User{ Username: username, Password: hashedRandomPassword, LockPassword: true, } setting.Defaults.Apply(user) // No restriction on Execute, Commands, or Admin

Compare with `http/auth.go` signup handler (lines 170-178):

d.settings.Defaults.Apply(user) user.Perm.Admin = false // Self-registered users should not inherit execution capabilities // from default settings, regardless of what the administrator has // configured as the default. user.Perm.Execute = false user.Commands = []string{}

The commit message for `b6a4fb1` states: "Execution rights must be explicitly granted by an admin." Users auto-created via proxy auth are also automatically provisioned (created on first login without explicit admin action), and the admin has not explicitly granted them execution rights.

## PoC

Test…