This also mean you don't technically even need this property to achieve this, you can also recompile a font with limited glyphs, this property just makes it easier to do this with an existing font file, though of course the user would be downloading a lot of unused glyphs.
https://research.securitum.com/stealing-data-in-great-style-...
This write-up demonstrates that OpenType contextual alternates are pretty powerful, but not as much as regular expressions.
jasonsb•4mo ago