Mozilla announced this week the release of Firefox 111, which patches over a dozen vulnerabilities, including potentially serious issues.

Of the 13 CVEs, seven have been assigned a ‘high’ severity rating. Three of them only impact Firefox for Android, and they can allow a hacker to hide fullscreen notifications — this can lead to user confusion or spoofing attacks — and open third-party apps without a prompt.

Other high-severity flaws patched with the latest Firefox updates can lead to arbitrary code execution and information disclosure. 

Cybersecurity firm Sophos has analyzed the patches and highlighted two vulnerabilities: CVE-2023-28161 and CVE-2023-28163. Sophos said in a blog post:

• CVE-2023-28161: One-time permissions granted to a local file were extended to other local files loaded in the same tab. With this bug, if you opened a local file (such as downloaded HTML content) that wanted access, say, to your webcam, then any other local file you opened afterwards would magically inherit that access permission without asking you. As Mozilla noted, this could lead to trouble if you were looking through a collection of items in your download directory – the access permission warnings you’d see would depend on the order in which you opened the files.
• CVE-2023-28163: Windows Save As dialog resolved environment variables. This is another keen reminder to sanitise thine inputs, as we like to say. In Windows commands, some character sequences are treated specially, such as %USERNAME%, which gets converted to the name of the currently logged-on user, or %PUBLIC%, which denotes a shared directory, usually in C:\Users. A sneaky website could use this as a way to trick you into seeing and approving the download of a filename that looks harmless but lands in a directory you wouldn’t expect (and where you might not later realise it had ended up). 

Cybersecurity agencies in Canada and the US have informed users about the latest Firefox patches, urging them to read the advisories and apply the necessary updates. 

Firefox vulnerabilities are not as targeted by threat actors as flaws affecting Chrome, but users should not ignore the potential risks. CISA’s known exploited vulnerabilities catalog lists 10 Firefox vulnerabilities discovered over the past decade.

In addition, Mozilla announced this week that it’s looking into making the Firefox Relay email and phone number masking tool available directly within Firefox.

Related: Emergency Firefox Update Patches Two Actively Exploited Zero-Day Vulnerabilities

Related: Firefox Updates Patch 10 High-Severity Vulnerabilities

Mozilla Patches High-Severity Vulnerabilities With Release of Firefox 111