Your Apple ID is only used for managing Photo Stream in Syncios. We don't collect any of your information like Apple ID, Photo Stream to our database. The use of your Apple ID on Syncios would not lead to your account security problem.
An Apple ID is the login ID which you can use to login different Apple features and services. Apple features and services that use your Apple ID: iCloud, iMessage, iBooks Store, Find My iPhone, iTunes Store, App Store, Game Center, Product Registration, iChat, Face Time, Apple TV, Cards.
If you are facing any trouble with your Apple ID, please contact Apple support for help.