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Just in case you haven't seen the postmortem of the Cloudflare outage which also was caused by a regex based DoS: https://blog.cloudflare.com/details-of-the-clo

• radiojosh 3y ago
  That was a great read, but there was one thing I didn't understand: Why would the regex string have "." twice in a row? What does ".." find that "." doesn't find? Does that just mean "at least two characters"?
  • rjbwork 3y ago
    It means specifically 2 characters, and is equivalent to .{2} ..+ or ...* are ways of writing "at least two characters".
  • bn-usd-mistake 3y ago
    A single `.` matches exactly one character. `..` matches exactly two characters (not more, not less).