Potential Captcha Validate Bypass in flask-session-captcha

flask-session-captcha is a package which allows users to extend Flask by adding an image based captcha stored in a server side session. In versions prior to 1.2.1, he `captcha.validate()` function would return `None` if passed no value (e.g. by submitting an having an empty form). If implementing users were checking the return value to be **False**, the captcha verification check could be bypassed. Version 1.2.1 fixes the issue. Users can workaround the issue by not explicitly checking that the value is False. Checking the return value less explicitly should still work.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

对函数返回值的检查不正确

flask-session-captcha 代码问题漏洞

flask-session-captcha是德国Joakim Uddholm个人开发者的一个 flask 的验证码实现。 flask-session-captcha 1.2.1之前版本存在安全漏洞，该漏洞源于如果没有传递任何值，`captcha.validate()`函数将返回`None`，如果返回值为**False**，则可以绕过验证码验证检查。

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