In recent Conversation with Mashable they confirmed they have altered the tweets and Facebook Post shared by Official Barack Obama’s Account. The tweets are added up with a video which depicts Graphic Violence and may be very gruesome for your comfort. Screenshots showing the Altered tweets and Facebook post:
  It is still not clear how SEA managed to alter those post, but experts believe SEA have access to URL shortener account which is used by Obama social media Accounts. One of the email account associated with Obama has also been compromised, a tweet with a screenshot mentioned, screenshot can be seen below, which can probably be associated with the campaign website hacked.
At the time of writing the Article the campaign website was restored, but the tweets and post On Facebook by Obama’s Official Accounts that contain the altered post can still be seen. The link posted by the SEA on their Twitter Account > OFA.BO/SEA now has been identified by Twitter has harmful and it has put a warning sign   

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