JavaScript is a scripting language used in web pages and applications, where flaws in code or dependencies can enable attacks and data theft.
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Background for this topic.
JavaScript is a programming language used to add behavior to web pages and to build applications that run outside the browser, including server-side services and tooling. In browsers, scripts can read and modify a page’s content and interact with available web APIs, subject to the browser’s security boundaries.
Its main security risks include cross-site scripting (XSS), in which attacker-controlled input is executed as page code, and DOM-based flaws caused by unsafe handling of data in client-side code. Third-party scripts and package dependencies also expand the code supply chain and may expose user data or introduce vulnerable behavior. Practical controls include context-aware output encoding, avoiding unsafe DOM sinks, restrictive Content-Security-Policy rules, and reviewing, pinning, and monitoring dependencies for vulnerabilities.
The owners of Polyfill.io have relaunched the JavaScript CDN service on a new domain after polyfill.io was shut down as researchers exposed it was delivering malicious code on upwards of 100,000 websites.. The Polyfill service claims that it has been "maliciously defamed" and been subject to "media messages slandering Polyfill." [...]
Google has taken steps to block ads for e-commerce sites that use the Polyfill.io service after a Chinese company acquired the domain and modified the JavaScript library ("polyfill.js") to redirect users to malicious and scam sites."Protecting our users is our top priority. We detected a security issue recently that may affect websites using certain third-party libraries," the company said in a
Over 100,000 sites have been impacted in a supply chain attack by the Polyfill.io service after a Chinese company acquired the domain and the script was modified to redirect users to malicious and scam sites. [...]
Injected malicious JavaScript code gives attackers administrator rights on websites, and fills sites with SEO spam.