Dear Steemit Friends,
I wanted to take this time to give my followers and all Steemit Users a heads up that a number of your Posting Keys may have been used without your knowledge. In the last several hours there have been a number of posts that have suddenly received a mass number of upvotes as well as posts with a mass number of downvotes, all within seconds of each other.
This was brought to my attention as well as other witnesses while we were chatting in Steem.Chat and is an update that I wanted to share with my fellow community members. Thanks, 
This could potentially be due to one of the many apps built on the Steem blockchain which users have granted posting authority to. Although this is not a regular occurrence, it can, and probably will happen so I urge everyone to be careful when selecting apps to trust your information with.
to be on the safe side, you should all check your voting history and look for posts that you may or may not have necessarily voted on. A number of posts will stand out if you have been impacted.
Since all users affected were using steemconnect only posting keys were used so your funds are safe. The recommendation is to review your authorizations and revoke any authorization to apps you do not use or recognize. It's best if you revoke all authorized apps in the meantime while the issue is being investigated and until the compromised app is identified and updates are made by the owner of the app.
If you need to review your app authorizations and/or revoke access, you can go to the following link:
https://v2.steemconnect.com/apps/authorized
It may also be advisable to update/change your Steemit password and keys.
Hopefully this is an isolated event and by working together we can find and patch the impacted app. As a community we should work together and protect one another. I hope this information helps and has potentially helped drive additional visibility towards security awareness and being more vigilant about who you share your information with.
Thanks for reading! Be safe!