Ugh, yup. This code should either be taken down, or come with a HUGE warning that it needs to be audited for security vulnerabilities.
CI strips out all funky characters, so while it is possible to cause an erroneous query, I'm not seeing a security issue here.
I would encourage you to consider trying hard to build a team around your project. In my experience open source software is hard work and really only can thrive in a community. This doesn't form magically around the software. It takes time and effort to build. If you can get good security folks in your community you can learn a lot from them.