Is iphone video downloader safe to use?

I downloaded "video downloader" From App Store. It allows you to download any video you want, while safari doesn't let you download them. So can I get any viruses by downloading any videos with this app? My iPhone 4s isn't jailbroken.

Depends what you mean by "safe". Apple ensures there aren't "viruses" in apps, but what they do allow is the developer to have your Phone Number, your e-mail address, your full name. If you do not find this "safe", it's too late, the app developer already HAS all that information about you.

Why do you think all of a sudden we're getting calls about "free cruises" on our smartphones even though "we" never gave our mobile number out to anyone? The app stole your mobile number and they sold it to telemarketers, there's a REASON why some apps are free, made to STEAL INFO.