Memory safety bugs present in Firefox 137, Thunderbird 137, Firefox ESR 128.9, and Thunderbird 128.9. 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. This vulnerability affects Firefox < 138, Firefox ESR < 128.10, Thunderbird < 138, and Thunderbird < 128.10.

A vulnerability was identified in Thunderbird where XPath parsing could trigger undefined behavior due to missing null checks during attribute access. This could lead to out-of-bounds read access and potentially, memory corruption. This vulnerability affects Firefox < 138, Firefox ESR < 128.10, Thunderbird < 138, and Thunderbird < 128.10.

Due to insufficient escaping of the special characters in the "copy as cURL" feature, an attacker could trick a user into using this command, potentially leading to local code execution on the user's system. *This bug only affects Firefox for Windows. Other versions of Firefox are unaffected.* This vulnerability affects Firefox ESR < 128.10, Firefox ESR < 115.23, and Thunderbird < 128.10.

A process isolation vulnerability in Thunderbird stemmed from improper handling of javascript: URIs, which could allow content to execute in the top-level document's process instead of the intended frame, potentially enabling a sandbox escape. This vulnerability affects Firefox < 138, Firefox ESR < 128.10, Firefox ESR < 115.23, Thunderbird < 138, and Thunderbird < 128.10.

Modification of specific WebGL shader attributes could trigger an out-of-bounds read, which, when chained with other vulnerabilities, could be used to escalate privileges. *This bug only affects Thunderbird for macOS. Other versions of Thunderbird are unaffected.* This vulnerability affects Firefox < 138, Firefox ESR < 128.10, Firefox ESR < 115.23, Thunderbird < 138, and Thunderbird < 128.10.

Thunderbird's update mechanism allowed a medium-integrity user process to interfere with the SYSTEM-level updater by manipulating the file-locking behavior. By injecting code into the user-privileged process, an attacker could bypass intended access controls, allowing SYSTEM-level file operations on paths controlled by a non-privileged user and enabling privilege escalation. This vulnerability affects Firefox < 138, Firefox ESR < 128.10, Firefox ESR < 115.23, Thunderbird < 138, and Thunderbird < 128.10.

A race condition existed in nsHttpTransaction that could have been exploited to cause memory corruption, potentially leading to an exploitable condition. This vulnerability affects Firefox < 137.0.2.

Memory safety bugs present in Firefox 136 and Thunderbird 136. 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. This vulnerability affects Firefox < 137 and Thunderbird < 137.

After selecting a malicious Windows `.url` shortcut from the local filesystem, an unexpected file could be uploaded. *This bug only affects Firefox on Windows. Other operating systems are unaffected.* This vulnerability affects Firefox < 137 and Thunderbird < 137.

Leaking of file descriptors from the fork server to web content processes could allow for privilege escalation attacks. This vulnerability affects Firefox < 137 and Thunderbird < 137.

An attacker could read 32 bits of values spilled onto the stack in a JIT compiled function. This vulnerability affects Firefox < 137 and Thunderbird < 137.

Memory safety bugs present in Firefox 136, Thunderbird 136, Firefox ESR 128.8, and Thunderbird 128.8. 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. This vulnerability affects Firefox < 137, Firefox ESR < 128.9, Thunderbird < 137, and Thunderbird < 128.9.

A crafted URL containing specific Unicode characters could have hidden the true origin of the page, resulting in a potential spoofing attack. This vulnerability affects Firefox < 137, Firefox ESR < 128.9, Thunderbird < 137, and Thunderbird < 128.9.

JavaScript code running while transforming a document with the XSLTProcessor could lead to a use-after-free. This vulnerability affects Firefox < 137, Firefox ESR < 115.22, Firefox ESR < 128.9, Thunderbird < 137, and Thunderbird < 128.9.

Following the recent Chrome sandbox escape (CVE-2025-2783), various Firefox developers identified a similar pattern in our IPC code. A compromised child process could cause the parent process to return an unintentionally powerful handle, leading to a sandbox escape. The original vulnerability was being exploited in the wild. *This only affects Firefox on Windows. Other operating systems are unaffected.* This vulnerability affects Firefox < 136.0.4, Firefox ESR < 128.8.1, and Firefox ESR < 115.21.1.

Malicious websites utilizing a server-side redirect to an internal error page could result in a spoofed website URL This vulnerability affects Firefox for iOS < 136.

Scanning certain QR codes that included text with a website URL could allow the URL to be opened without presenting the user with a confirmation alert first This vulnerability affects Firefox for iOS < 136.

Websites redirecting to a non-HTTP scheme URL could allow a website address to be spoofed for a malicious page This vulnerability affects Firefox for iOS < 136.

Memory safety bugs present in Firefox 135 and Thunderbird 135. 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. This vulnerability affects Firefox < 136 and Thunderbird < 136.

When String.toUpperCase() caused a string to get longer it was possible for uninitialized memory to be incorporated into the result string This vulnerability affects Firefox < 136 and Thunderbird < 136.