ECB

As Wikipeda handily illustrates with a picture of Tux, ECB doesn't do what you naively expect (because it can't) even when provided with a high quality block cipher primitive and a strong key.

There are a bunch of hard problems that ownCloud ought to want to solve. But solving already hard problems with PHP isn't going to happen, so they seem to have satisfied themselves with making it customisable, you can have the Wrong Thing™ in any flavour and colour scheme you like.