The Panama Papers leak was the result of an unpatched vulnerability in the popular content management systems: Drupal and WordPress. The ‘Panama Papers leak’ from Mossack Fonseca that exposed the tax-avoiding efforts by the world’s richest and most influential members was initially believed to be the result. Now, we are quite sure that the Panama Papers, which implicated 72 current and former heads of state, was due to vulnerabilities in both systems. The vulnerability affects up to 10000 Drupal websites, but not all sites will be affected.
Source: https://thehackernews.com/2016/07/drupal-security-update.html