Collected research

Bypassing Mozilla Port Blocking

Jeremiah Grossman · blog.jeremiahgrossman.com

Mozilla blocks several dozen TCP ports to stop the HTML Form Protocol Attack, but the block is applied only to the http protocol handler. Requesting ftp://host:22/ connects anyway — fast if the port is open, a timeout if not — restoring vertical port scanning beyond 80/443 for JavaScript and HTML-only scanners.

Record

Researcher

Jeremiah Grossman

Published by

blog.jeremiahgrossman.com

Topic

Other

In the archive

• Collected in the 2006 research round

Tags

• filter-bypass
• ftp
• url-parsing
• detection
• side-channel
• timing-attack
• owasp-a05-2021
• owasp-a09-2021

This page is the archive's own catalogue record. The research is the work of Jeremiah Grossman, first published at the original source. Preserved copies are kept so the citation survives its host; this one was last captured on 10 August 2026.