When using maxima w/ gnuplot, maxima creates ~/maxout.gnuplot_pipes file. That file is left when you quit maxima and pollutes the homedir. I believe maxima should use a proper temporary file for that.
Please provide a patch and/or move this issue upstream.
This is fixed in 5.44.0, but maxima's usage of /tmp is insecure. One step forward, two steps back.