The issue is related to the WebBrowserPersist component in Firefox, specifically with errors when executing the "Save Page As..." function. This can allow a remote attacker to gain unauthorized access to protected information. The internal WebBrowserPersist code does not use the correct origin context for a resource being saved, which manifests when sub-resources are loaded as part of the "Save Page As..." functionality. For example, a malicious page could recover a visitor's Windows username and NTLM hash by including resources otherwise unreachable to the malicious page. Similarly, SameSite cookies are sent on cross-origin requests when the "Save Page As..." menu item is selected to save a page.