Magnolia 5.3 reached end of life on June 30, 2017. This branch is no longer supported, see End-of-life policy.
To update Magnolia:
WEB-INF/libfolder of your old Magnolia instances with new JARs from the bundle.
indexfolder under each workspace directory:
repositories/magnolia/workspaces/<workspace>/index. Indexes are recreated on startup, which might take a while depending on the size of your repository.
magnolia.propertiesfiles, compare the changes to the file in the new bundle. Properties may have been added and removed.
Read the release notes for the version you are updating to and all intermediate versions.