Firefox 153 release notes for developers (Nightly)

Changes for web developers

Changes for add-on developers

• Extensions now require explicit user permission to access file:// URLs. Previously, access to local files was covered by the "Access your data for all websites" host permission. This change introduces a separate "Access local files on your computer" option in the extension's permissions settings (desktop only), and file access is turned off by default for all extensions, including existing ones. The extension.isAllowedFileSchemeAccess() method now correctly returns true if the user has granted file scheme access; previously, Firefox always returned false. Additionally, calling devtools.inspectedWindow.eval() on file:// URLs now requires this permission. (Firefox bug 2034168)

• Extension content scripts can now read and modify constructed stylesheets in document.adoptedStyleSheets and ShadowRoot.adoptedStyleSheets, without .wrappedJSObject. (Firefox bug 1751346)

Experimental web features

These features are shipping in Firefox 153 but are disabled by default. To experiment with them, search for the appropriate preference on the about:config page and set it to true. You can find more such features on the Experimental features page.