The U.S. Cybersecurity and Infrastructure Security Agency, known as CISA, has issued a critical warning concerning a remote code execution vulnerability in the Mirasvit Full Page Cache Warmer extension for Magento. This flaw, identified as CVE-2026-45247, is actively being exploited in attacks, posing significant risks to e-commerce platforms that rely on Magento. The vulnerability originates from insecure deserialization of untrusted data, particularly in how the extension processes serialized PHP objects through the CacheWarmer cookie. Attackers can exploit this by crafting malicious payloads sent via the cookie, allowing them to execute arbitrary code on the server without needing valid credentials. This makes it a severe threat to internet-facing Magento stores. Classified under CWE-502, the vulnerability is a common and dangerous flaw in web applications. Successful exploitation enables attackers to execute system commands, install backdoors, or further infiltrate the hosting environment. Due to Magento's widespread use, the potential impact is considerable. CISA has included this vulnerability in its Known Exploited Vulnerabilities catalog, requiring federal agencies to address it by June 6, 2026, following Binding Operational Directive 22-01. Although there is no official link to ransomware attacks, the flaw's nature makes it appealing to threat actors. Exploitation may involve suspicious HTTP requests with manipulated CacheWarmer cookies, leading to unexpected server processes or unauthorized file creation. To mitigate risks, organizations should apply vendor patches immediately. If no patch is available, disabling the affected component is recommended. Enhanced security measures include using web application firewalls to block malicious input and monitoring logs for unusual activity. This incident underscores the ongoing threat from insecure deserialization in web applications, emphasizing the need for timely patching and vigilant monitoring. Magento administrators should routinely assess third-party extensions for security compliance to prevent introducing vulnerabilities.