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Cybercriminals are building phishing pages that exist only inside victims’ browsers

Barracuda details a DocuSign-themed phishing campaign that renders login pages locally via blob URLs, abusing genuine Microsoft OAuth and Teams infrastructure.

Barracuda researchers describe a phishing campaign that starts with DocuSign-themed emails carrying calendar invites pointing to genuine Microsoft OAuth endpoints, then routes victims through Microsoft Teams to a resource hosted on cdn.bloom[.]io. The login page is assembled entirely inside the victim's browser from a blob URL, registers a service worker, and runs inside a sandboxed iframe that receives live instructions from the attacker's backend. Hidden command-and-control configuration indicates the page is part of a centrally managed phishing platform that can be updated and steered across many victims. Barracuda recommends phishing-resistant MFA such as FIDO2 keys or passkeys, monitoring of OAuth flows and redirect chains, and behavior-based identity controls rather than URL blocklisting.

Help Net Securityupdated · 6d agofirst · 6d agoPhishing & fraud in the wild 3 sources

New Phishing Attack Creates Malicious Pages Inside the Victim’s Browser

Barracuda details a phishing campaign that renders pages in-browser via blob URLs, routed through Microsoft Teams and cdn.bloom[.]io to evade detection.

Barracuda researchers analyzed a phishing campaign that generates a blob URL to render the phishing page entirely inside the victim's browser, leaving no static page for scanners to inspect. The chain begins with a Docusign-themed email containing a calendar invite, followed by a crafted redirect through Microsoft Teams to a resource on cdn.bloom[.]io that the browser converts into the blob URL. Service workers, iframes, and a hidden command-and-control configuration indicate the page is part of a centrally managed phishing platform that can be updated and steered across victims. Researchers recommend inspecting blob URL activity, monitoring OAuth authorization flows, and analyzing the full click path in email security controls.

SecurityWeek · 7d agoPhishing & fraud in the wild