Security vulnerabilities fixed in Firefox 63 — Mozilla

During HTTP Live Stream playback on Firefox for Android, audio data can be accessed across origins in violation of security policies. Because the problem is in the underlying Android service, this issue is addressed by treating all HLS streams as cross-origin and opaque to access. Note: this issue only affects Firefox for Android. Desktop versions of Firefox are unaffected.
When manipulating user events in nested loops while opening a document through script, it is possible to trigger a potentially exploitable crash due to poor event handling.
A potential vulnerability was found in 32-bit builds where an integer overflow during the conversion of scripts to an internal UTF-16 representation could result in allocating a buffer too small for the conversion. This leads to a possible out-of-bounds write. Note: 64-bit builds are not vulnerable to this issue.
By rewriting the Host request headers using the webRequest API, a WebExtension can bypass domain restrictions through domain fronting. This would allow access to domains that share a host that are otherwise restricted.
A vulnerability where a WebExtension can run content scripts in disallowed contexts following navigation or other events. This allows for potential privilege escalation by the WebExtension on sites where content scripts should not be run.
A WebExtension can request access to local files without the warning prompt stating that the extension will “Access your data for all websites” being displayed to the user. This allows extensions to run content scripts in local pages without permission warnings when a local file is opened.
By using the reflected URL in some special resource URIs, such as chrome:, it is possible to inject stylesheets and bypass Content Security Policy (CSP).
The internal WebBrowserPersist code does not use correct origin context for a resource being saved. This manifests when sub-resources are loaded as part of “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, if they can convince the visitor to save the complete web page. Similarly, SameSite cookies are sent on cross-origin requests when the “Save Page As…” menu item is selected to save a page, which can result in saving the wrong version of resources based on those cookies.
When a new protocol handler is registered, the API accepts a title argument which can be used to mislead users about which domain is registering the new protocol. This may result in the user approving a protocol handler that they otherwise would not have.
In private browsing mode on Firefox for Android, favicons are cached in the cache/icons folder as they are in non-private mode. This allows information leakage of sites visited during private browsing sessions. Note: this issue only affects Firefox for Android. Desktop versions of Firefox are unaffected.
Some special resource URIs will cause a non-exploitable crash if loaded with optional parameters following a ‘?’ in the parsed string. This could lead to denial of service (DOS) attacks.
If a site is loaded over a HTTPS connection but loads a favicon resource over HTTP, the mixed content warning is not displayed to users.
Mozilla developers and community members Christian Holler, Dana Keeler, Ronald Crane, Marcia Knous, Tyson Smith, Daniel Veditz, and Steve Fink reported memory safety bugs present in Firefox 62. Some of these bugs showed evidence of memory corruption and we presume that with enough effort that some of these could be exploited to run arbitrary code.
Mozilla developers and community members Christian Holler, Bob Owen, Boris Zbarsky, Calixte Denizet, Jason Kratzer, Jed Davis, Taegeon Lee, Philipp, Ronald Crane, Raul Gurzau, Gary Kwong, Tyson Smith, Raymond Forbes, and Bogdan Tara reported memory safety bugs present in Firefox 62 and Firefox ESR 60.2. Some of these bugs showed evidence of memory corruption and we presume that with enough effort that some of these could be exploited to run arbitrary code.