URL scanning services are widely used in security workflows to detect malicious websites and protect users from online threats. However, their common practice of publicly indexing scanned URLs may unintentionally expose sensitive user information through URL-embedded access credentials. Although isolated accounts of such privacy incidents exist, a systematic assessment of their prevalence is still lacking. We present leakylinks, an automated analysis pipeline that combines URL filtering with LLM-driven semantic classification to identify URLs exposing Sensitive Personal Information (SPI). Using LEAKYLINKS, we analyze URLs collected from public feeds of six prominent URL scanning services over a period of three weeks. With the framework, we visited 332k URLs, identifying over 4 k URLs which leak SPI with a precision of 97 %. To further assess the extent to which published URLs are actively accessed by third parties, we deploy honeypages and submit their links to the selected URL scanning services. Our measurements confirm that external entities access URLs submitted to these scanners, often from potentially suspicious IPs exhibiting behavior commonly associated with reconnaissance or opportunistic probing. Taken together, these findings indicate that URL scanning services represent a valuable target for web adversaries and may already be subject to active exploitation in the wild.

Browser extensions are third-party add-ons that provide myriads of features to their users while browsing on the Web. Extensions often interact with the websites a user visits and perform various operations such as DOM-based manipulation, script injections, and so on. However, this also enables nefarious websites to track their visitors by fingerprinting extensions. Researchers in the past have shown that extensions are susceptible to fingerprinting based on the resources they include, the styles they deploy, or the DOM-based modifications they perform. Fortunately, the current extension ecosystem contains safeguards against many such known issues through appropriate defense mechanisms.

Browser extensions enhance the functionality of native Web applications on the client side. They provide a rich end-user experience by utilizing feature-rich JavaScript APIs, otherwise inaccessible for native applications. However, prior studies suggest that extensions may degrade the client-side security to execute their operations, such as by altering the DOM, executing untrusted scripts in the applications' context, and performing other security-critical operations for the user.