Chinese hackers are already exploiting a ‘fully weaponized’ software vulnerability that is causing mayhem on the web, with experts warning that it is the ‘most serious threat they have seen in decades. The flaw was uncovered earlier this month in a piece of software called Log4j, which helps applications interact with one another across computer networks. By exploiting the flaw, dubbed Log4Shell, hackers can take control of servers that run the network and repurpose them for their own ends. That could mean stealing data on those servers such as medical records and photos, plundering company databases for people’s bank details,…