WEB project security?

Question

Information Security

What should be considered and what should be paid attention to when checking the security of a web project?
Certificate, validation of inputs (I set 3, html, js, php) + checking each input using regular expressions and the presence of words from the black list, so I doubt that you can enter malicious code. Uploading files was excluded in the project, everything is more difficult with their virus checks.
What else? And I would also like to know what words, phrases, symbols should be added to the black list?

Answer 1

Uploading files was excluded in the project, everything is more difficult with their virus checks. What else?

Requests to the server - also exclude. :)
But seriously, this is a multi-level system and you need to validate all user data according to the "white" list of templates.
Reliable website protection against most types of attacks