Update Dockerfile

Dockerfile

@@ -15,7 +15,11 @@ RUN apt-get update && apt-get install --no-install-recommends -y \
 # Create and set the working directory
 RUN mkdir /var/www
 RUN mkdir /var/www/tmp
-RUN chmod +w /var/www/tmp
+RUN chmod a+w /var/www/tmp
+
+RUN groupadd -r flaskuser && useradd -r -g flaskuser flaskuser
+USER flaskuser
+
 ENV HOME /var/www
 WORKDIR /var/www
 COPY . /var/www