It seems that Android users should be cautious even if they use apps from well known companies, such as Skype. Androidpolice just found the Skype app stores private information without encryption and sets wrong permissions on those files, so other apps can easily access these information and do whatever they want to do. Androidpolice actually released a toy app to demonstrate their findings.
To protect your personal information, we advise users to take care in selecting which applications to download and install onto their device.
So if you have an Android with Skype installed, listen to their advice. How to select safe applications? Sorry, I don’t know.
Whether it is a good idea for androidpolice to make this public before Skype issues a fix is debatable. However, I don’t understand why Android depends on app developers to set file permissions. Why not just give each app a completely isolated environment, so an app cannot access data in other apps? If an app has to share something, it can implement a content provider. I’m not sure if a content provider has better protection or access control on the data it shares. Maybe Android developers know better about this.
Anyway, be careful.