PHP is the underlying computer code used in 70% of websites and businesses have been warned to take immediate action to apply the IT update to address a critical security issue that may allow hackers to execute commands on any web server running PHP.  

The National Cyber Security Centre (NCSC) warned the security issue could allow an attacker to trigger an out-of-memory (OOM) condition in PHP that results in memory corruption. Under certain conditions, this corruption could be exploited to achieve unauthenticated remote code execution.