#1269 new
Peter Hilton

CAPTCHA example contans security vulnerability

Reported by Peter Hilton | November 20th, 2011 @ 02:23 PM

Reported by Daniel Dekany | August 23rd, 2011 @ 01:31 PM (moved from www.playframework.org project)

Here: http://www.playframework.org/documentation/1.2.1/guide5
You have this:

public static void captcha(String id) {
    Images.Captcha captcha = Images.captcha();
    String code = captcha.getText("#E4EAFD");
    Cache.set(id, code, "10mn");
    renderBinary(captcha);
}

Since the ID comes from an URL, the visitor can overwrite whatever cached value with whose name is known (not random).

I think there's yet another vulnerability in the example code (didn't double check it, but I'm certainly right). If someone solves a CAPTCHA, they can re-use the solution to solve other CAPTCHA-s by sending the same randomID as earlier. So a human solves the CAPTCHA, then using the randomID and the solution can flood the site with a program. You should delete the cache entry after checking to fix this.
I'm sure many users blindly copy-paste from the documentation, so it's probably important to fix these.

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