Security Vulnerabilities fixed in Firefox ESR 91.11 — Mozilla

A malicious website that could create a popup could have resized the popup to overlay the address bar with its own content, resulting in potential user confusion or spoofing attacks. This bug only affects Firefox for Linux. Other operating systems are unaffected.
Session history navigations may have led to a use-after-free and potentially exploitable crash.
An iframe that was not permitted to run scripts could do so if the user clicked on a javascript: link.
In the nsTArray_Impl::ReplaceElementsAt() function, an integer overflow could have occurred when the number of elements to replace was too large for the container.
An attacker could have injected CSS into stylesheets accessible via internal URIs, such as resource:, and in doing so bypass a page’s Content Security Policy.
If there was a PAC URL set and the server that hosts the PAC was not reachable, OCSP requests would have been blocked, resulting in incorrect error pages being shown.
The ms-msdt, search, and search-ms protocols deliver content to Microsoft applications, bypassing the browser, when a user accepts a prompt. These applications have had known vulnerabilities, exploited in the wild (although we know of none exploited through Firefox), so in this release Firefox has blocked these protocols from prompting the user to open them.This bug only affects Firefox on Windows. Other operating systems are unaffected.
If an object prototype was corrupted by an attacker, they would have been able to set undesired attributes on a JavaScript object, leading to privileged code execution.
The Mozilla Fuzzing Team reported potential vulnerabilities present in Firefox 101 and Firefox ESR 91.10. 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.