One Click From a Forged Signature: The Flaws in Belgium's Digital Identity System- 321

August 11, 2026

Two million Belgians rely on a browser extension called Connective to prove who they are online — to their bank, to government agencies, and to anyone who needs a legally binding electronic signature. For an unknown period before a researcher found the problem, that same extension would talk to any website that asked it to, with no way of confirming who was actually on the other end of the conversation. The flaws, disclosed at DEF CON by James Arnott, founder of the cybersecurity firm Bay Area Labs, sat in software developed by Nitro Software Belgium and used by eight of the country's ten largest banks and more than sixty government agencies — precisely the population for whom digital identity and electronic signatures are supposed to be uniquely trustworthy.

The root cause was almost architectural in its simplicity: Connective never verified which website was actually attempting to communicate with the application running on a user's machine. Because that check was missing, any website — or, just as easily, any embedded online advertisement loaded inside a completely unrelated page — could interact directly with Connective without the user's knowledge or consent. Arnott found that a malicious site could silently read a connected electronic ID card's details and payment card information straight out of the application. Worse, an attacker could trigger authentication pop-ups styled to look official, and because Connective let web pages customize the text displayed inside those dialog boxes without ever showing which domain had actually requested them, a user had no reliable way to tell a legitimate prompt from a phishing attempt. Whatever PIN a victim typed into one of these prompts was transmitted straight back to the requesting webpage — at which point an attacker holding that PIN could generate unauthorized approval tokens and, whenever the victim's physical eID card happened to be sitting in a card reader, forge a legally binding electronic signature in their name.

The damage from that alone extends well beyond Connective's own user base, because Belgium's broader digital-identity ecosystem is built on the assumption that an eID signature means what it claims to mean. Government portals like CSAM.be and third-party identity providers such as Itsme carried no vulnerabilities of their own, but both rely on eID signatures to register and authenticate accounts — meaning an attacker holding a forged signature could use it to register or hijack a digital identity account on services that had done nothing wrong beyond trusting a credential Connective was quietly handing out to whoever asked. Arnott's research went further still, uncovering a separate remote-code-execution vulnerability that required no eID card to be present at all: by exploiting a flaw in how Connective processed files on the local machine, a malicious website could force the application to execute attacker-controlled code at the user's own privilege level, triggered simply by visiting a page and downloading a file disguised as an ordinary document. Because the exploit needed no special permissions to work, it also carried the structural risk of a self-propagating worm — an attacker could hijack a victim's own credentials to automatically send the same malicious link onward to their contacts, each new click reproducing the same silent compromise.

Nitro fully remediated the vulnerabilities 146 days after Arnott's initial report, deploying updates that block unauthorized origin requests and secure how the application handles PIN entry, with final enforcement completed in late July — a resolution timeline that earned the researcher a $200 bug bounty and, as far as public records show, no formal CVE designation for either flaw. Nitro has not responded to requests for comment on the case. The gap between the severity of what Arnott found — silent identity theft, forgeable legally binding signatures, and a wormable remote-code-execution path, all reachable from an ordinary webpage or embedded ad — and the modesty of both the bounty and the near-total public silence around it is its own kind of finding: a piece of software sitting at the center of a national digital-identity system operated, for an unknown stretch of time, on the assumption that no one would ever bother to check whether it was talking to the right website at all.