It recently came to our attention that a list of approximately 1,000 Minecraft account names and passwords were made freely available on the internet. We believe this list consists of information collected by a group of malicious users from a well known "griefing team". How the information in this list was obtained is not sure, but we suspect they collected them through the use of hacked clients (that pretend to only give you extra features like flying or seeing through blocks but actually send your account information to the creators as well) or websites made to look like the official Minecraft site.
Given this information, we feel we need to stress that people make sure to only use Minecraft client mods that they absolutely trust and are verified by the community. While this issue brings to the light the malicious opportunities client modders have, we want to stress that many client mods found within the community are not malicious. We believe people should be healthily skeptic but not overly paranoid as to whether or not a client mod is stealing your information. Unless you're using a sketchy client that allows you to cheat, for example, you should be safe.