Firefox will accept any registered Program ID as an external protocol handler and offer to launch this local application when given a matching URL on Windows operating systems. This should only happen if the program has specifically registered itself as a "URL Handler" in the Windows registry. *Note: This issue only affects Windows operating systems. Other operating systems are unaffected.*. This vulnerability affects Thunderbird < 60.6, Firefox ESR < 60.6, and Firefox < 66.

Bugzilla 2.16rc1 through 2.22.7, 3.0.x through 3.3.x, 3.4.x before 3.4.12, 3.5.x, 3.6.x before 3.6.6, 3.7.x, 4.0.x before 4.0.2, and 4.1.x before 4.1.3 does not prevent changes to the confirmation e-mail address (aka old_email field) for e-mail change notifications, which makes it easier for remote attackers to perform arbitrary address changes by leveraging an unattended workstation.

The location bar in Firefox for Android can be spoofed by forcing a user into fullscreen mode, blocking its exiting, and creating of a fake location bar without any user notification. Note: This issue only affects Firefox for Android. Other versions and operating systems are unaffected. This vulnerability affects Firefox < 50.

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.

A spoofing vulnerability can occur when a malicious site with an extremely long domain name is opened in an Android Custom Tab (a browser panel inside another app) and the default browser is Firefox for Android. This could allow an attacker to spoof which page is actually loaded and in use. Note: this issue only affects Firefox for Android. Other versions and operating systems are unaffected. This vulnerability affects Firefox < 59.

Mozilla Firefox before 43.0 mishandles the # (number sign) character in a data: URI, which allows remote attackers to spoof web sites via unspecified vectors.

Visual truncation vulnerability in Mozilla Firefox before 3.0.14, and 3.5.x before 3.5.3, allows remote attackers to trigger a vertical scroll and spoof URLs via unspecified Unicode characters with a tall line-height property.

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.

Punycode format text will be displayed for entire qualified international domain names in some instances when a sub-domain triggers the punycode display instead of the primary domain being displayed in native script and the sub-domain only displaying as punycode. This could be used for limited spoofing attacks due to user confusion. This vulnerability affects Firefox < 57.

A spoofing vulnerability can occur when a page switches to fullscreen mode without user notification, allowing a fake address bar to be displayed. This allows an attacker to spoof which page is actually loaded and in use. Note: This attack only affects Firefox for Android. Other operating systems are not affected. This vulnerability affects Firefox < 56.

On pages containing an iframe, the "data:" protocol can be used to create a modal dialog through Javascript that will have an arbitrary domains as the dialog's location, spoofing of the origin of the modal dialog from the user view. Note: This attack only affects installations with e10 multiprocess turned off. Installations with e10s turned on do not support the modal dialog functionality. This vulnerability affects Firefox < 56.

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.

Characters from the "Canadian Syllabics" unicode block can be mixed with characters from other unicode blocks in the addressbar instead of being rendered as their raw "punycode" form, allowing for domain name spoofing attacks through character confusion. The current Unicode standard allows characters from "Aspirational Use Scripts" such as Canadian Syllabics to be mixed with Latin characters in the "moderately restrictive" IDN profile. We have changed Firefox behavior to match the upcoming Unicode version 10.0 which removes this category and treats them as "Limited Use Scripts.". This vulnerability affects Firefox < 54, Firefox ESR < 52.2, and Thunderbird < 52.2.

URLs containing certain unicode glyphs for alternative hyphens and quotes do not properly trigger punycode display, allowing for domain name spoofing attacks in the location bar. This vulnerability affects Thunderbird < 45.7, Firefox ESR < 45.7, and Firefox < 51.

An attack can use a blob URL and script to spoof an arbitrary addressbar URL prefaced by "blob:" as the protocol, leading to user confusion and further spoofing attacks. This vulnerability affects Firefox < 52.

Android intents can be used to launch Firefox for Android in reader mode with a user specified URL. This allows an attacker to spoof the contents of the addressbar as displayed to users. Note: This attack only affects Firefox for Android. Other operating systems are not affected. This vulnerability affects Firefox < 53.

When dragging content from the primary browser pane to the addressbar on a malicious site, it is possible to change the addressbar so that the displayed location following navigation does not match the URL of the newly loaded page. This allows for spoofing attacks. This vulnerability affects Firefox < 52.

A malicious site could spoof the contents of the print preview window if popup windows are enabled, resulting in user confusion of what site is currently loaded. This vulnerability affects Firefox < 52 and Thunderbird < 52.

The combined, single character, version of the letter 'i' with any of the potential accents in unicode, such as acute or grave, can be spoofed in the addressbar by the dotless version of 'i' followed by the same accent as a second character with most font sets. This allows for domain spoofing attacks because these combined domain names do not display as punycode. This vulnerability affects Firefox < 57.

Default fonts on OS X display some Tibetan characters as whitespace. When used in the addressbar as part of an IDN this can be used for domain name spoofing attacks. Note: This attack only affects OS X operating systems. Other operating systems are unaffected. This vulnerability affects Firefox < 54, Firefox ESR < 52.2, and Thunderbird < 52.2.

Low descenders on some Tibetan characters in several fonts on OS X are clipped when rendered in the addressbar. When used as part of an Internationalized Domain Name (IDN) this can be used for domain name spoofing attacks. Note: This attack only affects OS X operating systems. Other operating systems are unaffected. This vulnerability affects Firefox < 58.

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.

The displayed addressbar URL can be spoofed on Firefox for Android using a javascript: URI in concert with JavaScript to insert text before the loaded domain name, scrolling the loaded domain out of view to the right. This can lead to user confusion. *This vulnerability only affects Firefox for Android < 62.*

Several fonts on OS X display some Tibetan and Arabic characters as whitespace. When used in the addressbar as part of an IDN this can be used for domain name spoofing attacks. Note: This attack only affects OS X operating systems. Other operating systems are unaffected. This vulnerability affects Firefox < 56, Firefox ESR < 52.4, and Thunderbird < 52.4.

The destructor function for the "WindowsDllDetourPatcher" class can be re-purposed by malicious code in concert with another vulnerability to write arbitrary data to an attacker controlled location in memory. This can be used to bypass existing memory protections in this situation. Note: This attack only affects Windows operating systems. Other operating systems are not affected. This vulnerability affects Thunderbird < 52.3, Firefox ESR < 52.3, and Firefox < 55.

SVG loaded through "<img>" tags can use "<meta>" tags within the SVG data to set cookies for that page. This vulnerability affects Firefox < 57.

When entered directly, Reader Mode did not strip the username and password section of URLs displayed in the addressbar. This can be used for spoofing the domain of the current page. This vulnerability affects Firefox < 54.

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.

A mechanism to spoof the Firefox for Android addressbar using a "javascript:" URI. On Firefox for Android, the base domain is parsed incorrectly, making the resulting location less visibly a spoofed site and showing an incorrect domain in appended notifications. This vulnerability affects Firefox < 53.

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.