The vulnerability exists because of an improper authorization check in the Api.set_config_value function. The ADMIN_ONLY_CORE_OPTIONS set, which is used to restrict access to security-sensitive settings, is missing the ("general", "ssl_verify") entry. This allows any authenticated user with the SETTINGS permission to disable TLS certificate validation by setting ssl_verify to off.
The exploit chain starts when a non-admin user makes an API call to set_config_value to change this setting. Later, when pyload needs to make an outbound HTTPS request, the RequestFactory.get_options function reads this malicious setting. Finally, the HttpRequest.prepare function consumes this setting and disables pycurl's SSL_VERIFYPEER and SSL_VERIFYHOST options, making the connection vulnerable to a Man-in-the-Middle (MITM) attack. An attacker can then intercept the traffic and present a forged certificate, which pyload would accept.