Add captcha type verification to sign-up page

[andrixnet]

On June 21st a complaint was received by the hosting of OCUS claiminig that the server has sent SPAM to a certain destination domain.
While the complaint is quite thin (actually only 2 messages were sent in total and given the context of the investigation one was likely a registration confirmation email), it has revealed a legitimate potential vulnerability.
The sign-up page does not have a captcha / anti-bot verification.

The object of this issue is to add a captcha type anti-bot verification to the sign-up page.
Furthermore, given the open-source nature of the project and volunteer based hosting for individual sites, I request that such protection be implemented in a standalone and independent way within the project's code, that is not to use third party service providers for it to work. (ie excluding services like reCAPTCHA and similar).

Thank you.

[rapotek]

I understand you require the captcha to be generated and verified inside project code, but to clarify: will you accept the captcha generated inside opencaching website node using external library f.ex. incorporated by composer or do you insist to have the captcha generator written as a part of the project code from scratch?

[andrixnet]

In my opinion it can be either (with the choice of an existing library being simpler), as long the following criteria are met:

• the code or library is open-source
• it is included at the development stage (ie. does not require individual site admins to install additional software)
• it is entirely self-hosted (including all dependencies)
• it does not depend on any third party / external service(s) and/or resources at runtime
  (ie external to the OC hosting server)

Thank you.