Avcontent.db. Arbitrary Delete.
The PlayStation Vita has a few apps for displaying various media formats. primarily the Photos, Videos, and Music applications, you can load images into these apps media files require "promotion" to be put into these apps
basically each of the media apps has a sqllite3 database called 'avcontent.db' inside various folders on ux0 which cache the contents of these apps.
By editing the avcontent.db you can change the path of any media contents to be whatever path you want if you then delete it inside the app, it will not only delete the entry from the database, but it will delete that underlying file as well.
Using the videos app i was able to read arbitrary files by changing the path in the avcontent.db, and then copying it with CMA, however this only worked with files inside ux0: files outside there would not work, i am not sure why.
Ultimately this trick is kinda useless, it requires having access to the memory card to write a hacked avcontent.db in the first place, which if you had you can delete whatever you want anyway? (it could also be done with CMA i guess), so it'd only be useful for removing files from say ur0. or ones you cant do via backups / restore or with another hacked vita) but at that point you may as well just delete the file you want from the memory card using that,
an interesting idea is to setup a SQL Trigger on delete to automatically put the entry back into the database, this way you could delete any file over and over again. this could be used to make a sort of 'unlink memory card' feature, that works even without hacks. but by the time i had this idea, there was already h-encore2..