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 Windows systems, the logger run by the Windows updater deletes the file "update.log" before it runs in order to write a new log of that name. The path to this file is supplied at the command line to the updater and could be used in concert with another local exploit to delete a different file named "update.log" instead of the one intended. Note: This attack only affects Windows operating systems. Other operating systems are not affected. 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.

On Windows systems, if non-null-terminated strings are copied into the crash reporter for some specific registry keys, stack memory data can be copied until a null is found. This can potentially contain private data from the local system. Note: This attack only affects Windows operating systems. Other operating systems are not affected. This vulnerability affects 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.

A buffer overflow can occur when manipulating Accessible Rich Internet Applications (ARIA) attributes within the DOM. 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 when reading an image observer during frame reconstruction after the observer has been freed. This results in a potentially exploitable crash. This vulnerability affects Thunderbird < 52.3, Firefox ESR < 52.3, and Firefox < 55.

If a long user name is used in a username/password combination in a site URL (such as " http://UserName:Password@example.com"), the resulting modal prompt will hang in a non-responsive state or crash, causing a denial of service. This vulnerability affects Firefox < 55.