position: sticky not working correctly inside position: fixed container

Hello Firefox Support Team, I would like to report a browser compatibility issue regarding CSS positioning behavior that differs from Chromium-based browsers. **Issue Description:** When an element with `position: sticky` is placed inside a container with `position: fixed`, Firefox treats the sticky element as if it has `position: relative`, effectively breaking the sticky positioning functionality. **Expected Behavior:** The sticky element should maintain its sticky positioning behavior even when nested inside a fixed-positioned container, as it does in Chromium-based browsers. **Current Firefox Behavior:** The sticky element loses its sticky properties and behaves like a relatively positioned element. **Use Case:** This issue particularly affects modal implementations where: - The `body` element receives `position: fixed` to prevent background scrolling - Page elements (such as `.total-section`) should maintain their sticky behavior regardless of changes to the body positioning **Browser Comparison:** - **Chromium browsers (Chrome):** Sticky positioning works correctly in this scenario - **Firefox:** Sticky positioning fails and falls back to relative behavior **Request:** Could you please consider aligning Firefox's behavior with other major browsers? The current inconsistency creates cross-browser compatibility issues and forces developers to implement JavaScript workarounds. Thanks!