How Reasonable Decisions Created a Security Incident
November 26, 2026
Shiodome Building 18F, 1-2-20 Kaigan, Minato City, Tokyo
〒105-0022 Tokyo, Minato City, Kaigan, 1 Chome−2−20 汐留ビルディング 18F
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Please take note that the venue for this event is OPTiM Tokyo!
Agenda
18:30 〜 19:00 Doors open
Grab a drink, grab some stickers, and catch up with your fellow Rubyists.
19:00 ~ 19:05 Opening
We'll kick things off by welcoming everyone and giving a short introduction of the event.
19:05 ~ 19:10 OPTiM Lightning Talk
We'll take a moment to hear a quick word from our sponsor.
19:10 〜 19:40 How Reasonable Decisions Created a Security Incident -
Paul McMahon
A security incident exposed the resumes of 460 job seekers. The surprising part? There was no single bug or obviously wrong decision to blame. Instead, a series of reasonable technical choices interacted in unexpected ways, creating a vulnerability that went unnoticed until it was too late. In this talk, I’ll share how the incident was discovered, investigated, and resolved, along with practical lessons on security, complexity, and hidden assumptions in Ruby on Rails applications.
Profile
Paul McMahon is the founder of TokyoDev and has been building Ruby on Rails applications for over 20 years. He also founded the Tokyo Rubyist Meetup in 2010, and previously co-founded the event platform Doorkeeper. Today he runs TokyoDev, helping international software developers advance their careers in Japan, while staying hands-on with the development and operation of the site’s Rails application.
19:40 〜 20:00 Rubyist show and tell
Do you have a cool snippet of Ruby code that you'd like to share, but it doesn't warrant an entire presentation? A challenge with your Ruby application you've been struggling with, and would like some advice? A helpful library or tool you've come across? This is your chance to share it.
For those who'd like to participate, you'll have up to five minutes. There's no need to create a slide deck, but you'll be able to use the projector if you have a code sample or something else to share. While we'll ask you if you'd like to participate when signing up, this is just to gauge…
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