This might make sense when asking a stranger for directions or for someone to help with your car problem, because the relationship is 1:1.
But this breaks down in contexts where scale is a factor.
When assisting users of your project, the relationship is 1:many. And if the project is popular, it is unfair to expect the author to be helping so many people.
Of the people with whom you have formed strong social bonds, yes.
Of random strangers? .. I don't think so.
Unless they are bound by some sort of a contract (employees, servants, etc).
The alternative brought to it's logical conclusion is Shkreli and rasing medicine prices by thousand percent.
The perfect example is yours, "this project does not take security into consideration. Use at your own responsibility. You should probably start with securing this_X, that_Y, and that_Z.".
Another example could be "this is a POC and does not go kindly on system resources. You might want to scale back the number of simultaneously opened sockets for any real use."
> to be honest about the project
Sometimes you see the attitude "You get what you pay for", but putting code in the ecosystem without property explaining what it is is like littering.
In the same way I want to be able to walk in the park without constantly checking the ground for dog shit, I want to be able to use software without having to audit every part personally because the author didn't care for it, or communicate that fact.
You don't have any duties or obligation towards any individual to assist them with their issues.
The only obligations you have is to be honest about the project. For example, if you know that the project is not written with security in mind, you must announce the fact, so that people don't go using the project assuming you took care of all potential exploits.
Beyond that, you have no obligations towards anyone. Quite the opposite. You've already done your part. You donated the product of your effort for free. The obligation is on people who use your product. If they want you to care of their issues, they are obliged to give something back in return. At the very least, appreciation.