CVE-2026-0887 is a security vulnerability identified in the PDF Viewer component of Mozilla Firefox, affecting versions earlier than 147 and Firefox ESR versions earlier than 140.7. The vulnerability is characterized as a clickjacking issue that can lead to information disclosure. Clickjacking involves tricking a user into clicking on something different from what the user perceives, potentially revealing sensitive information or triggering unintended actions. In this case, the vulnerability allows an attacker to overlay or disguise UI elements within the PDF Viewer, enabling them to capture or leak information from PDF documents rendered in the browser. The flaw does not require prior authentication but does require user interaction, such as clicking on a manipulated interface element. No public exploits have been reported yet, but the vulnerability is significant due to Firefox's widespread use across personal, corporate, and governmental environments. The absence of a CVSS score limits precise quantification of risk, but the nature of the vulnerability suggests a high impact on confidentiality, with moderate complexity for exploitation. The vulnerability is particularly concerning for environments where sensitive or confidential PDF documents are frequently accessed via Firefox, as attackers could leverage this flaw to extract information without the user's knowledge. Mozilla has published the vulnerability details but has not yet provided patch links, indicating that updates to Firefox 147 and ESR 140.7 or later versions are the expected remediation.

For European organizations, the primary impact of CVE-2026-0887 is the potential compromise of confidentiality through unauthorized information disclosure from PDF documents viewed in Firefox. This could affect sectors such as finance, healthcare, legal, and government agencies where sensitive documents are routinely accessed. The vulnerability could be exploited to leak personal data, intellectual property, or classified information, leading to regulatory compliance issues under GDPR and other data protection laws. The attack requires user interaction, which may limit large-scale automated exploitation but does not eliminate risk, especially in targeted phishing or social engineering campaigns. The widespread use of Firefox in Europe, including in public sector and enterprise environments, increases the attack surface. Additionally, organizations using Firefox ESR versions for stability and long-term support may be slower to update, prolonging exposure. The lack of known exploits reduces immediate risk but does not preclude future exploitation. Overall, the vulnerability could undermine trust in document confidentiality and lead to reputational damage and financial losses if exploited.

European organizations should prioritize updating all Firefox installations to version 147 or ESR 140.7 or later as soon as these versions are available and verified. Until updates are applied, organizations should consider restricting access to sensitive PDF documents via Firefox or using alternative browsers not affected by this vulnerability. Implementing browser security policies that disable or limit the use of the built-in PDF Viewer can reduce exposure. User awareness training should emphasize caution when interacting with unexpected or suspicious PDF content, especially in emails or web links. Network-level controls such as web filtering to block malicious sites hosting crafted PDFs can provide additional defense. Security teams should monitor for any emerging exploit attempts related to this vulnerability and apply threat intelligence feeds accordingly. Finally, organizations should review and enhance their incident response plans to address potential information disclosure incidents stemming from browser vulnerabilities.