WhatsApp Discloses File Spoofing, Arbitrary URL Scheme Vulnerabilities

Summary

Meta disclosed two medium-impact vulnerabilities in WhatsApp that were patched earlier in 2026. CVE-2026-23863 affects Windows versions and allows attackers to spoof file attachments as harmless files while executing as executables; CVE-2026-23866 affects iOS and Android, allowing arbitrary URL scheme handlers to be triggered via malicious Instagram Reels. Both flaws were responsibly disclosed through Meta's bug bounty program with no evidence of active exploitation.

Full text

Meta-owned WhatsApp has published two new security advisories describing vulnerabilities that were patched earlier this year in the popular messaging app. One of the vulnerabilities is CVE-2026-23863, a medium-impact attachment spoofing issue affecting WhatsApp for Windows prior to version 2.3000.1032164386.258709. An attacker could have exploited the flaw to create a maliciously formatted document with embedded NUL bytes in the file name. When sent as an attachment, the recipient would see it as a harmless file, but it would run as an executable when opened, WhatsApp’s advisory explains. The second vulnerability, CVE-2026-23866, has also been assigned a ‘medium impact’ rating. It affects WhatsApp for iOS (v2.25.8.0-v2.26.15.72) and WhatsApp for Android (v2.25.8.0-v2.26.7.10). According to WhatsApp, incomplete validation of AI rich response messages for Instagram Reels could have allowed an attacker to “trigger processing of media content from an arbitrary URL on another user’s device, including triggering OS-controlled custom URL scheme handlers.” WhatsApp has not shared additional information, but such custom URL scheme vulnerabilities in real-world attack scenarios may allow threat actors to redirect users to phishing sites, and launch other apps and services on the device via URL schemes such as facetime:, tel:, itms-apps:, or custom app deep links.Advertisement. Scroll to continue reading. WhatsApp said both vulnerabilities were responsibly disclosed by unnamed researchers through the Meta bug bounty program. The company says there is no evidence of exploitation in the wild. Related: $1M WhatsApp Hack Flops: Only Low-Risk Bugs Disclosed to Meta After Pwn2Own Withdrawal Related: Researcher Discovers 4th WhatsApp View Once Bypass; Meta Won’t Patch Related: Vulnerability Allowed Scraping of 3.5 Billion WhatsApp Accounts Related: WhatsApp Boosts Account Security for At-Risk Individuals Written By Eduard Kovacs Eduard Kovacs (@EduardKovacs) is senior managing editor at SecurityWeek. He worked as a high school IT teacher before starting a career in journalism in 2011. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering. 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Indicators of Compromise

• cve — CVE-2026-23863
• cve — CVE-2026-23866

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