Hackers possibly linked to the Kremlin exploited previously patched iOS and Android flaws in an attempt to hack visitors of multiple websites, including one celebrating the 250th anniversary of American independence, researchers said Wednesday. The attackers, which the researchers assessed with “moderate to high confidence” were part of Russia’s Foreign Intelligence Service, targeted other sites, many with links to that country’s ongoing war against Ukraine. The attacks began when iPhone or Android users visited one of potentially hundreds of different sites…