Sites can bypass security checks on permissions to install lightweight themes by manipulating the "baseURI" property of the theme element. This could allow a malicious site to install a theme without user interaction which could contain offensive or embarrassing images. This vulnerability affects Thunderbird < 52.8, Thunderbird ESR < 52.8, Firefox < 60, and Firefox ESR < 52.8.

If cursor visibility is toggled by script using from 'none' to an image and back through script, the cursor will be rendered temporarily invisible within Firefox. Note: This vulnerability only affects OS X. Other operating systems are not affected. This vulnerability affects Firefox < 58.

If Media Capture and Streams API permission is requested from documents with "data:" or "blob:" URLs, the permission notifications do not properly display the originating domain. The notification states "Unknown protocol" as the requestee, leading to user confusion about which site is asking for this permission. This vulnerability affects Firefox < 59.

An audio capture session can started under an incorrect origin from the site making the capture request. Users are still prompted to allow the request but the prompt can display the wrong origin, leading to user confusion about which site is making the request to capture an audio stream. This vulnerability affects Firefox < 58.

A lack of parameter validation on IPC messages results in a potential out-of-bounds write through malformed IPC messages. This can potentially allow for sandbox escape through memory corruption in the parent process. This vulnerability affects Thunderbird < 52.7, Firefox ESR < 52.7, and Firefox < 59.

In the Windows 10 April 2018 Update, Windows Defender SmartScreen honors the "SEE_MASK_FLAG_NO_UI" flag associated with downloaded files and will not show any UI. Files that are unknown and potentially dangerous will be allowed to run because SmartScreen will not prompt the user for a decision, and if the user is offline all files will be allowed to be opened because Windows won't prompt the user to ask what to do. Firefox incorrectly sets this flag when downloading files, leading to less secure behavior from SmartScreen. Note: this issue only affects Windows 10 users running the April 2018 update or later. It does not affect other Windows users or other operating systems. This vulnerability affects Thunderbird < 52.8, Thunderbird ESR < 52.8, Firefox < 60, and Firefox ESR < 52.8.

Mozilla Firefox before 40.0 and Firefox ESR 38.x before 38.2 do not impose certain ECMAScript 6 requirements on JavaScript object properties, which allows remote attackers to bypass the Same Origin Policy via the reviver parameter to the JSON.parse method.

Mozilla Firefox before 36.0 does not properly recognize the equivalence of domain names with and without a trailing . (dot) character, which allows man-in-the-middle attackers to bypass the HPKP and HSTS protection mechanisms by constructing a URL with this character and leveraging access to an X.509 certificate for a domain with this character.

In 32-bit versions of Firefox, the Adobe Flash plugin setting for "Enable Adobe Flash protected mode" is unchecked by default even though the Adobe Flash sandbox is actually enabled. The displayed state is the reverse of the true setting, resulting in user confusion. This could cause users to select this setting intending to activate it and inadvertently turn protections off. This vulnerability affects Firefox < 60.

The filename appearing in the "Downloads" panel improperly renders some Unicode characters, allowing for the file name to be spoofed. This can be used to obscure the file extension of potentially executable files from user view in the panel. Note: the dialog to open the file will show the full, correct filename and whether it is executable or not. This vulnerability affects Firefox < 60.

Mozilla Firefox before 30.0 and Thunderbird through 24.6 on OS X do not ensure visibility of the cursor after interaction with a Flash object and a DIV element, which makes it easier for remote attackers to conduct clickjacking attacks via JavaScript code that produces a fake cursor image.

The Pocket toolbar button, once activated, listens for events fired from it's own pages but does not verify the origin of incoming events. This allows content from other origins to fire events and inject content and commands into the Pocket context. Note: this issue does not affect users with e10s enabled. This vulnerability affects Firefox ESR < 45.6 and Firefox < 50.1.

WebExtensions can bypass security checks to load privileged URLs and potentially escape the WebExtension sandbox. This vulnerability affects Firefox < 50.

The "Mark of the Web" was not correctly saved on Windows when files with very long names were downloaded from the Internet. Without the Mark of the Web data, the security warning that Windows displays before running executables downloaded from the Internet is not shown. Note: This attack only affects Windows operating systems. Other operating systems are unaffected. This vulnerability affects Firefox < 54, Firefox ESR < 52.2, and Thunderbird < 52.2.

It is possible to spoof the sender's email address and display an arbitrary sender address to the email recipient. The real sender's address is not displayed if preceded by a null character in the display string. This vulnerability affects Thunderbird < 52.5.2.