Security Vulnerabilities fixed in Firefox 84 — Mozilla

When a BigInt was right-shifted the backing store was not properly cleared, allowing uninitialized memory to be read.
Certain blit values provided by the user were not properly constrained leading to a heap buffer overflow on some video drivers.
The lifecycle of IPC Actors allows managed actors to outlive their manager actors; and the former must ensure that they are not attempting to use a dead actor they have a reference to. Such a check was omitted in WebGL, resulting in a use-after-free and a potentially exploitable crash.
Certain input to the CSS Sanitizer confused it, resulting in incorrect components being removed. This could have been used as a sanitizer bypass.
When flex-basis was used on a table wrapper, a StyleGenericFlexBasis object could have been incorrectly cast to the wrong type. This resulted in a heap user-after-free, memory corruption, and a potentially exploitable crash.
When a malicious application installed on the user’s device broadcast an Intent to Firefox for Android, arbitrary headers could have been specified, leading to attacks such as abusing ambient authority or session fixation. This was resolved by only allowing certain safe-listed headers.Note: This issue only affected Firefox for Android. Other operating systems are unaffected.
When a HTTPS pages was embedded in a HTTP page, and there was a service worker registered for the former, the service worker could have intercepted the request for the secure page despite the iframe not being a secure context due to the (insecure) framing.
By attempting to connect a website using an unresponsive port, an attacker could have controlled the content of a tab while the URL bar displayed the original domain. Note: This issue only affects Firefox for Android. Other operating systems are unaffected.
Using techniques that built on the slipstream research, a malicious webpage could have exposed both an internal network’s hosts as well as services running on the user’s local machine.
When a user typed a URL in the address bar or the search bar and quickly hit the enter key, a website could sometimes capture that event and then redirect the user before navigation occurred to the desired, entered address. To construct a convincing spoof the attacker would have had to guess what the user was typing, perhaps by suggesting it.
When an extension with the proxy permission registered to receive , the proxy.onRequest callback was not triggered for view-source URLs. While web content cannot navigate to such URLs, a user opening View Source could have inadvertently leaked their IP address.
If a user downloaded a file lacking an extension on Windows, and then “Open”-ed it from the downloads panel, if there was an executable file in the downloads directory with the same name but with an executable extension (such as .bat or .exe) that executable would have been launched instead.Note: This issue only affected Windows operating systems. Other operating systems are unaffected.
Mozilla developer Christian Holler reported memory safety bugs present in Firefox 83 and Firefox ESR 78.5. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code.
Mozilla developers Christian Holler, Jan-Ivar Bruaroey, and Gabriele Svelto reported memory safety bugs present in Firefox 83. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code.