As I was quick checking
Cryptomator, I happened to notice the portable is still v1.5.11-5 -- so, unsurprisingly, after I launched it and set it to look for updates it stated there was newer v1.5.13 available.
I was able to manually update it by downloading the installer, (
Uni)extracting and replacing the corresponding files in the portable's sub-folders '
app', '
app\app' and '
app\runtime'.
That last folder is where the portable Java runtime is stored and required an additional trick: after copying files over and replacing existing ones, go to explorer's selection menu ("
Home | Selection" in the ribbon bar) and click "
Invert selection", then delete the obsolete files.
It still works and shows the updated version. Total disk cost is about 86MB.