One reason I still not use DDG is no support for language specific search (settings not work). It mixed many similar language in the search result, for example, english and spanish.
Still have no idea what's the "unfixed security issues", and few guys mention about it.
I image there the "security issues" will be (if it exist):
1. because key are easy to stolen by coolboot or trojan.
2. because it has backdoor, will save key to a hidden place.
3. because it will leave some information in other place, like 2 but it's implantation problem.
4. because it use a vulnerable algorithm to generate key.
5. because pbkdf2 or aes256 is broken but nobody known it.
exclude 2 and 3, change to other software it's not help at all, algorithm almost same.