A hacker gained remote access to a Florida city’s water treatment plant in an attempt to contaminate the city’s supply of water with a harmful chemical, authorities say. The amount of sodium hydroxide in the water supply briefly increased from about 100 parts per million to 11,100. The FBI and Secret Service have joined the Pinellas County Sheriff’s Office in onsite response to the attack. Officials say the hacker likely exploited cybersecurity weaknesses, including poor password security and an outdated computer operating system.