Medium

Spoofing in Firefox DOM Copy & Paste and Drag & Drop

IdentifiersCVE-2026-0890CWE-290· Authentication Bypass by Spoofing

CVE-2026-0890 is a spoofing vulnerability in Mozilla's DOM: Copy & Paste and Drag & Drop component affecting Firefox before 147, Firefox ESR before 140.7, Thunderbird before 147, and Thunderbird ESR before 140.7. The issue allows copied/pasted or dragged/dropped DOM content to be misrepresented, creating conditions where user-visible content or the apparent source/semantics of transferred content can be spoofed. Based on the available advisory text, the flaw is limited to spoofing behavior in DOM handling rather than memory corruption or code execution.

For your environment

Are you exposed to this one?

Mallory correlates every CVE against your assets, your vendors, and active adversary campaigns. Know which vulnerabilities matter for you, not just which ones are loud.

Start free trial

ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation can enable user deception by causing copied, pasted, dragged, or dropped DOM content to appear as something other than its true origin or meaning. This could facilitate phishing-style workflows, UI deception, or misrepresentation of content in browser or mail-client contexts. The provided material does not indicate direct code execution, privilege escalation, or sandbox escape from this CVE.

Mitigation

If you can’t patch tonight, do this now.

If immediate patching is not possible, reduce exposure to untrusted web content and untrusted message content, especially in workflows that rely on drag-and-drop or copy-paste operations. In high-risk environments, restrict browsing to trusted sites, use additional application or OS containment controls, and where operationally feasible, limit or avoid drag-and-drop/copy-paste interactions involving sensitive data until updates are applied.

Remediation

Patch, then assume compromise.

Upgrade to a fixed version. Mozilla fixed the issue in Firefox 147, Firefox ESR 140.7, Thunderbird 147, and Thunderbird ESR 140.7. On Debian-derived systems, apply the relevant security updates for affected firefox-esr or thunderbird packages as provided by the distribution.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType

MozillaFirefoxapplication

MozillaThunderbirdapplication

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

7 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

7 SOURCESView more in app

cyber security newsNews

Jan 15, 2026

Firefox 147 Released With Fixes for 16 Vulnerabilities that Enable Arbitrary Code Execution

Spoofing issue in DOM copy/paste and drag-and-drop handling (low severity).

What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.

Start free trial

Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity4