Spoofing issue in the Downloads Panel component. This vulnerability was fixed in Firefox 146, Thunderbird 146, Firefox ESR 140.7, and Thunderbird 140.7.

Spoofing issue in WebExtensions. This vulnerability was fixed in Firefox 151 and Thunderbird 151.

Truncation of a long URL could have allowed origin spoofing in a permission prompt. This vulnerability affects Firefox < 132, Firefox ESR < 128.4, Thunderbird < 128.4, and Thunderbird < 132.

A lack of in app notification for entering fullscreen mode could have lead to a malicious website spoofing browser chrome.<br>*This bug only affects Firefox Focus. Other versions of Firefox are unaffected.*. This vulnerability affects Firefox < 110 and Firefox ESR < 102.8.

A clipboard "paste" button could persist across tabs which allowed a spoofing attack. This vulnerability affects Firefox < 132, Firefox ESR < 128.4, Thunderbird < 128.4, and Thunderbird < 132.

Mitigation bypass in Firefox for Android. This vulnerability was fixed in Firefox 150.

Incorrect code generation could have led to unexpected numeric conversions and potential undefined behavior.*Note:* This issue only affects 32-bit ARM devices. This vulnerability affects Firefox < 123, Firefox ESR < 115.8, and Thunderbird < 115.8.

When combining CSS properties for overflow and transform, the mouse cursor could interact with different coordinates than displayed. This vulnerability affects Firefox ESR < 102.1, Firefox ESR < 91.12, Firefox < 103, Thunderbird < 102.1, and Thunderbird < 91.12.

Spoofing issue in the Popup Blocker component. This vulnerability was fixed in Firefox 151 and Thunderbird 151.

Information disclosure, mitigation bypass in the Privacy component in Firefox for Android. This vulnerability was fixed in Firefox 143.

In a non-standard configuration of Firefox, an integer overflow could have occurred based on network traffic (possibly under influence of a local unprivileged webpage), leading to an out-of-bounds write to privileged process memory. *This bug only affects Firefox if a non-standard preference allowing non-HTTPS Alternate Services (`network.http.altsvc.oe`) is enabled.* This vulnerability affects Firefox < 118.

When resizing a popup while requesting fullscreen access, the popup would have become unable to leave fullscreen mode. This vulnerability affects Firefox ESR < 91.5, Firefox < 96, and Thunderbird < 91.5.

If an insecure element was added to a page after a delay, Firefox would not replace the secure icon with a mixed content security status This vulnerability affects Firefox for iOS < 124.

A malicious Android application could craft an Intent that would have been processed by Firefox for Android and potentially result in a file overwrite in the user's profile directory. One exploitation vector for this would be to supply a user.js file providing arbitrary malicious preference values. Control of arbitrary preferences can lead to sufficient compromise such that it is generally equivalent to arbitrary code execution.<br> *Note: This issue only affects Firefox for Android. Other operating systems are unaffected.*. This vulnerability affects Firefox ESR < 68.7.

When the number of cookies per domain was exceeded in `document.cookie`, the actual cookie jar sent to the host was no longer consistent with expected cookie jar state. This could have caused requests to be sent with some cookies missing. This vulnerability affects Firefox < 116, Firefox ESR < 102.14, and Firefox ESR < 115.1.

A crafted S/MIME message consisting of an inner encryption layer and an outer SignedData layer was shown as having a valid digital signature, although the signer might have had no access to the contents of the encrypted message, and might have stripped a different signature from the encrypted message. Previous versions had only suppressed showing a digital signature for messages with an outer multipart/signed layer. This vulnerability affects Thunderbird < 68.1.1.

Incorrect boundary conditions in the Graphics: WebGPU component. This vulnerability was fixed in Firefox 145 and Thunderbird 145.

JIT miscompilation in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 143.0.3.

Thunderbird allowed the Text Direction Override Unicode Character in filenames. An email attachment could be incorrectly shown as being a document file, while in fact it was an executable file. Newer versions of Thunderbird will strip the character and show the correct file extension. This vulnerability affects Thunderbird < 115.0.1 and Thunderbird < 102.13.1.

An attacker could write data to the user's clipboard, bypassing the user prompt, during a certain sequence of navigational events. This vulnerability affects Firefox < 129, Firefox ESR < 128.3, and Thunderbird < 128.3.

Firefox normally asks for confirmation before asking the operating system to find an application to handle a scheme that the browser does not support. It did not ask before doing so for the Usenet-related schemes news: and snews:. Since most operating systems don't have a trusted newsreader installed by default, an unscrupulous program that the user downloaded could register itself as a handler. The website that served the application download could then launch that application at will. This vulnerability affects Firefox < 130, Firefox ESR < 128.2, and Firefox ESR < 115.15.

Documents formed using data: URLs in an OBJECT element failed to inherit the CSP of the creating context. This allowed the execution of scripts that should have been blocked, albeit with a unique opaque origin. This vulnerability affects Firefox < 76.

When checking if the Browsing Context had been discarded in `HttpBaseChannel`, if the load group was not available then it was assumed to have already been discarded which was not always the case for private channels after the private session had ended. This vulnerability affects Firefox < 117, Firefox ESR < 115.2, and Thunderbird < 115.2.

A website could have obscured the full screen notification by using the file open dialog. This could have led to user confusion and possible spoofing attacks. This vulnerability affects Firefox < 116, Firefox ESR < 115.2, and Thunderbird < 115.2.

Spoofing issue in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.

Spoofing issue in the Privacy: Anti-Tracking component. This vulnerability was fixed in Firefox 149 and Thunderbird 149.

Spoofing issue in the WebAuthn component in Firefox for Android. This vulnerability was fixed in Firefox 148 and Thunderbird 148.

A malicious extension could have opened a popup window lacking an address bar. The title of the popup lacking an address bar should not be fully controllable, but in this situation was. This could have been used to spoof a website and attempt to trick the user into providing credentials. This vulnerability affects Firefox ESR < 78.9, Firefox < 87, and Thunderbird < 78.9.

Spoofing issue in Firefox. This vulnerability was fixed in Firefox 145, Firefox ESR 140.5, and Firefox ESR 115.30.

Spoofing issue in the DOM: Copy & Paste and Drag & Drop component. This vulnerability was fixed in Firefox 147, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7.

When opening a website using the `firefox://` protocol handler, SameSite cookies were not properly respected. This vulnerability affects Firefox < 123.

Spoofing issue in the Toolbar component in Firefox for Android. This vulnerability was fixed in Firefox 151.

Through a series of API calls and redirects, an attacker-controlled alert dialog could have been displayed on another website (with the victim website's URL shown). This vulnerability affects Firefox < 123, Firefox ESR < 115.8, and Thunderbird < 115.8.

The incorrect domain may have been displayed in the address bar during an interrupted navigation attempt. This could have led to user confusion and possible spoofing attacks. This vulnerability affects Firefox < 133 and Thunderbird < 133.

Spoofing issue in the WebAuthn component in Firefox for Android. This vulnerability was fixed in Firefox 143 and Thunderbird 143.

When exiting fullscreen mode, an iframe could have confused the browser about the current state of fullscreen, resulting in potential user confusion or spoofing attacks. This vulnerability affects Thunderbird < 91.10, Firefox < 101, and Firefox ESR < 91.10.

An attacker could cause a select dropdown to be shown over another tab; this could have led to user confusion and possible spoofing attacks. This vulnerability affects Firefox < 133, Firefox ESR < 128.5, Thunderbird < 133, and Thunderbird < 128.5.

After a website had entered fullscreen mode, it could have used a previously opened popup to obscure the notification that indicates the browser is in fullscreen mode. Combined with spoofing the browser chrome, this could have led to confusing the user about the current origin of the page and credential theft or other attacks. This vulnerability affects Firefox < 74.

Thunderbird parses addresses in a way that can allow sender spoofing in case the server allows an invalid From address to be used. For example, if the From header contains an (invalid) value "Spoofed Name ", Thunderbird treats spoofed@example.com as the actual address. This vulnerability was fixed in Thunderbird 128.10.1 and Thunderbird 138.0.1.

Certain crafted MIME email messages that claimed to contain an encrypted OpenPGP message, which instead contained an OpenPGP signed message, were wrongly shown as being encrypted. This vulnerability was fixed in Thunderbird 136 and Thunderbird 128.8.

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

When a JavaScript URL (javascript:) is evaluated and the result is a string, this string is parsed to create an HTML document, which is then presented. Previously, this document's URL (as reported by the document.location property, for example) was the originating javascript: URL which could lead to spoofing attacks; it is now correctly the URL of the originating document. This vulnerability affects Firefox < 74.

A missing delay in popup notifications could have made it possible for an attacker to trick a user into granting permissions. This vulnerability affects Firefox < 113, Firefox ESR < 102.11, and Thunderbird < 102.11.

A user who enables full-screen mode on a specially crafted web page could potentially be prevented from exiting full screen mode. This may allow spoofing of other sites as the address bar is no longer visible. *This bug only affects Firefox Focus for Android. Other versions of Firefox are unaffected.* This vulnerability affects Firefox < 131.

Websites could utilize Javascript links to spoof URL addresses in the Focus navigation bar This vulnerability affects Focus for iOS < 130.

If a site had been granted the permission to open popup windows, it could cause Select elements to appear on top of another site to perform a spoofing attack. This vulnerability affects Firefox < 130, Firefox ESR < 128.2, and Thunderbird < 128.2.

Fleet is open source device management software. Prior to version 4.80.1, a vulnerability in Fleet's IP extraction logic allows unauthenticated attackers to bypass API rate limiting by spoofing client IP headers. This may allow brute-force login attempts or other abuse against Fleet instances exposed to the public internet. Fleet extracted client IP addresses from request headers (`True-Client-IP`, `X-Real-IP`, `X-Forwarded-For`) without validating that those headers originate from a trusted proxy. The extracted IP is used as the key for rate limiting and IP ban decisions. As a result, an attacker could rotate the value of these headers on each request, causing Fleet to treat each attempt as coming from a different client. This effectively bypasses per-IP rate limits on sensitive endpoints such as the login API, enabling unrestricted brute-force or credential stuffing attacks. This issue primarily affects Fleet instances that are directly exposed to the internet without a reverse proxy that overwrites forwarded-IP headers. Instances behind a properly configured proxy or WAF are less affected. Version 4.80.1 contains a patch. If an immediate upgrade is not possible, administrators should ensure Fleet is deployed behind a reverse proxy (e.g., nginx, Cloudflare, AWS ALB) that overwrites `X-Forwarded-For` with the true client IP, and apply rate limiting at the proxy or WAF layer.

WebCTRL systems that communicate over BACnet inherit the protocol's lack of network layer authentication. WebCTRL does not implement additional validation of BACnet traffic so an attacker with network access could spoof BACnet packets directed at either the WebCTRL server or associated AutomatedLogic controllers. Spoofed packets may be processed as legitimate.

OpenClaw's voice-call plugin versions before 2026.2.3 contain an improper authentication vulnerability in webhook verification that allows remote attackers to bypass verification by supplying untrusted forwarded headers. Attackers can spoof webhook events by manipulating Forwarded or X-Forwarded-* headers in reverse-proxy configurations that implicitly trust these headers.

An issue was discovered in 6.0 before 6.0.4, 5.2 before 5.2.13, and 4.2 before 4.2.30. `ASGIRequest` allows a remote attacker to spoof headers by exploiting an ambiguous mapping of two header variants (with hyphens or with underscores) to a single version with underscores. Earlier, unsupported Django series (such as 5.0.x, 4.1.x, and 3.2.x) were not evaluated and may also be affected. Django would like to thank Tarek Nakkouch for reporting this issue.