Like any other file (including PDF), DjVu files can be injected with malicious content. This is not to say that you should steer clear of these files. DjVu is an excellent file extension that allows the user to store a lot of compressed content in one place. So, like with any other file, be careful whom you get your DjVu files from, put them through an antimalware, and don’t download any files unless they’re from trusted sources.