Ignore comment in Regex

Background

Brakeman version: 4.10.0 Rails version: 6.0.3.4 Ruby version: 2.7.2

False Positive

Full warning from Brakeman:

Category: Format Validation
Check: ValidationRegex
Message: Insufficient validation for `payment_pointer` using `/
    \A                # start
    \$                # starts with a dollar sign
    ([a-zA-Z0-9\-.])+ # matches the hostname (ex ilp.uphold.com)
    (\/[\x20-\x7F]+)?  # optional forward slash and identifier with printable ASCII characters
    \z # end
  /x`. Use `\A` and `\z` as anchors

Why might this be a false positive?

The above expression use \A and \z, but still considered as invalid. It will pass if remove the last comment #end. Since the expression worked with the option \\\x, the comment and space will be ignored and not influence the expression. Therefore the validation should consider ignoring them as well.