I designed a small webapp (I would rather call it browserApp) that helps me to automate a task. Now, I don't need a webserver to host this app as it is merely using js, jquery and other js libraries to run it in my browser which is good enough for me, plus, does not make use of databases or another tier like an apache web server and makes no use of backend code. I added some security features like sanitation of character, etc, that will only protect from crashing (there is not data saved after the process is done, so there is no db to reach, everything in client-side of course).
I'm trying to understand the security considerations of having this small tool running from time to time on my browser. It seems harmless but in my experience "seeming" leads to the opposite in reality.