A use-after-free vulnerability can occur when an editor DOM node is deleted prematurely during tree traversal while still bound to the document. This results in a potentially exploitable crash. This vulnerability affects Thunderbird < 52.3, Firefox ESR < 52.3, and Firefox < 55.

A content security policy (CSP) "frame-ancestors" directive containing origins with paths allows for comparisons against those paths instead of the origin. This results in a cross-origin information leak of this path information. This vulnerability affects Firefox < 55.

A mechanism that uses AppCache to hijack a URL in a domain using fallback by serving the files from a sub-path on the domain. This has been addressed by requiring fallback files be inside the manifest directory. This vulnerability affects Thunderbird < 52.3, Firefox ESR < 52.3, and Firefox < 55.

A use-after-free vulnerability can occur when the layer manager is freed too early when rendering specific SVG content, resulting in a potentially exploitable crash. This vulnerability affects Firefox < 55.

During TLS 1.2 exchanges, handshake hashes are generated which point to a message buffer. This saved data is used for later messages but in some cases, the handshake transcript can exceed the space available in the current buffer, causing the allocation of a new buffer. This leaves a pointer pointing to the old, freed buffer, resulting in a use-after-free when handshake hashes are then calculated afterwards. This can result in a potentially exploitable crash. This vulnerability affects Firefox < 56, Firefox ESR < 52.4, and Thunderbird < 52.4.

When a page's content security policy (CSP) header contains a "sandbox" directive, other directives are ignored. This results in the incorrect enforcement of CSP. This vulnerability affects Thunderbird < 52.3, Firefox ESR < 52.3, and Firefox < 55.

A use-after-free vulnerability can occur when manipulating the DOM during the resize event of an image element. If these elements have been freed due to a lack of strong references, a potentially exploitable crash may occur when the freed elements are accessed. This vulnerability affects Thunderbird < 52.3, Firefox ESR < 52.3, and Firefox < 55.

A use-after-free vulnerability can occur while re-computing layout for a "marquee" element during window resizing where the updated style object is freed while still in use. This results in a potentially exploitable crash. This vulnerability affects Thunderbird < 52.3, Firefox ESR < 52.3, and Firefox < 55.

A use-after-free vulnerability can occur in WebSockets when the object holding the connection is freed before the disconnection operation is finished. This results in an exploitable crash. This vulnerability affects Thunderbird < 52.3, Firefox ESR < 52.3, and Firefox < 55.

JavaScript in the "about:webrtc" page is not sanitized properly being assigned to "innerHTML". Data on this page is supplied by WebRTC usage and is not under third-party control, making this difficult to exploit, but the vulnerability could possibly be used for a cross-site scripting (XSS) attack. This vulnerability affects Firefox < 55.

The Developer Tools feature suffers from a XUL injection vulnerability due to improper sanitization of the web page source code. In the worst case, this could allow arbitrary code execution when opening a malicious page with the style editor tool. This vulnerability affects Firefox ESR < 52.3 and Firefox < 55.

Response header name interning does not have same-origin protections and these headers are stored in a global registry. This allows stored header names to be available cross-origin. This vulnerability affects Firefox < 55.

On Linux systems, if the content process is compromised, the sandbox broker will allow files to be truncated even though the sandbox explicitly only has read access to the local file system and no write permissions. Note: This attack only affects the Linux operating system. Other operating systems are not affected. This vulnerability affects Firefox < 55.

A use-after-free vulnerability can occur in the Fetch API when the worker or the associated window are freed when still in use, resulting in a potentially exploitable crash. This vulnerability affects Firefox < 56, Firefox ESR < 52.4, and Thunderbird < 52.4.

A buffer overflow will occur when viewing a certificate in the certificate manager if the certificate has an extremely long object identifier (OID). This results in a potentially exploitable crash. This vulnerability affects Thunderbird < 52.3, Firefox ESR < 52.3, and Firefox < 55.

On pages containing an iframe, the "data:" protocol can be used to create a modal alert that will render over arbitrary domains following page navigation, spoofing of the origin of the modal alert from the iframe content. This vulnerability affects Thunderbird < 52.3, Firefox ESR < 52.3, and Firefox < 55.

If a server sends two Strict-Transport-Security (STS) headers for a single connection, they will be rejected as invalid and HTTP Strict Transport Security (HSTS) will not be enabled for the connection. This vulnerability affects Firefox < 55.

When an "iframe" has a "sandbox" attribute and its content is specified using "srcdoc", that content does not inherit the containing page's Content Security Policy (CSP) as it should unless the sandbox attribute included "allow-same-origin". This vulnerability affects Firefox < 55.

Same-origin policy protections can be bypassed on pages with embedded iframes during page reloads, allowing the iframes to access content on the top level page, leading to information disclosure. This vulnerability affects Thunderbird < 52.3, Firefox ESR < 52.3, and Firefox < 55.

A buffer overflow can occur when the image renderer attempts to paint non-displayable SVG elements. This results in a potentially exploitable crash. This vulnerability affects Thunderbird < 52.3, Firefox ESR < 52.3, and Firefox < 55.