Hello Firefox Support, I am experiencing a consistent and disruptive performance issue that occurs immediately after certain complex web pages (particularly those with heavy scripting or dynamic content) have fully loaded. The symptom is a temporary but complete freeze of the Firefox window, often lasting between 5 to 10 seconds, during which time the browser is completely unresponsive. This freeze is accompanied by a significant spike in CPU usage (often reaching 90-100%, according to Task Manager/Activity Monitor). Details: Trigger: The freeze reliably occurs right after the page status changes from "Loading" to "Done." I suspect it is related to post-load scripting execution or rendering finalization. Impact: Any ongoing user interaction is halted until the spike subsides. Tested Scenarios: I have replicated this on multiple sites, including heavy news aggregators, social media feeds, and complex web applications. Troubleshooting: This issue persists even after: Clearing cache and cookies. Running Firefox in Safe Mode (disabling all extensions). Creating a new, clean Firefox profile. This severely degrades the browsing experience, especially when quickly navigating between tabs or starting a session. Could you please investigate potential issues within the core rendering engine or script execution scheduler that might be causing these severe post-load processing bottlenecks? Thank you.