Data breaches happen all too often, but it's rare that they target your browser's sync service... and unfortunately, Opera just became one of those exceptions. The company is warning users that it detected a hack in its sync system that may have given intruders access to login details. While your passwords are likely safe (all synced passwords are encrypted, for example), Opera isn't risking anything. It's resetting all sync account passwords, and it recommends that you change any linked third-party passwords to be on the safe side.
Opera is quick to note that the majority of its 350 million users won't be affected, since most don't use sync. However, this still leaves about 1.7 million active users at risk, and there are likely more inactive users who are storing useful passwords. True, it's doubtful that the breach will lead to serious damage, but this certainly isn't the kind of news Opera would want following its sale to a Chinese security giant.