Top all-time · #654
Mattias Geniar
Personal blog · ma.ttias.beprogrammingsecurity
Mattias Geniar's personal blog at ma.ttias.be covers programming and security. Since 2014, 95 different Hacker News readers have linked it 419 times, most often “Terminal escape sequences – the new XSS for Linux sysadmins”. It is still writing: the last post was on 2026-11-01, and you can follow it by feed.
Sometimes recommended · 6 of 40 sampled comments recommend it?
Why HN links it
HN readers link this blog for practical sysadmin posts on Linux, SSH, TLS and HTTP/2, and for security advisories and mitigations. Commenters also name its weekly newsletter, cron.weekly.
- Recommended for · 6 comments
- Named as a blog and newsletter to follow; an HTTP/2 guide 'really useful'; a unikernel article helpful.
Summarised by Claude from a sample of 40 HN comments that link here. Each comment is marked recommending, critical or neutral (citing without judging); how this works.
Mattias Geniar, co-founder of Oh Dear. A decade of writing on Linux, PHP, DevOps, web performance, security and the open web, plus talks and projects.
Most-linked posts?
- Terminal escape sequences – the new XSS for Linux sysadmins5 people · 8 mentions · first linked 2015-09-24
- The Cron.weekly Newsletter5 people · 5 mentions · first linked 2019-12-15
- There’s more than one way to write an IP address5 people · 5 mentions · first linked 2019-07-09
- Google’s QUIC protocol: moving the web from TCP to UDP4 people · 7 mentions · first linked 2016-08-01
- Create a SOCKS proxy on a Linux server with SSH to bypass content filters4 people · 5 mentions · first linked 2017-01-19
- Despite revoked CA’s, StartCom and WoSign continue to sell certificates3 people · 3 mentions · first linked 2017-01-17
- How I write and curate the cron.weekly newsletter (2020)3 people · 3 mentions · first linked 2020-05-01
- Show HN: Traffic numbers (stats and graphs) for an HN frontpage link3 people · 3 mentions · first linked 2015-01-19
- Varnish Explained3 people · 3 mentions · first linked 2016-10-20
- Show IDN Punycode in Firefox to Avoid Phishing URLs3 people · 3 mentions · first linked 2018-02-19
What Hacker News says?
Damnit, they found my loop-hole! https://ma.ttias.be/loophole-cookie-notices/
Comment linking /loophole-cookie-notices/
on “No Cookie for You”Submitted Remote Kernel Code Execution Via HTTP Request In IIS On Windows as a story · 458 points
HN discussionI'm keeping a list [1] of all the (possible) precautions one can take, ahead of the patches appearing in a few hours. Exploits are now circulating, according to Cloudflare's CTO, so _any_ mitigation is worth investigating https://ma.ttias.be/php-cve-2026-109618-early-mitigation/
Comment linking /php-cve-2026-109618-early-mitigation/
on “Security advisory: Critical remote code execution vulnerabilities, update now”Submitted Why some governments appear not to be acting on the Covid-19 threat as a story · 309 points
HN discussionOpenSSH also includes a SOCKS proxy which you can use with no additional software: https://ma.ttias.be/socks-proxy-linux-ssh-bypass-content-fil... Whether it grants you any significant anonymity is debatable, but it works well for evading content filters and tunneling your traffic onto a more trustworthy network.
Comment linking /socks-proxy-linux-ssh-bypass-content-filters/
on “NordVPN confirms it was hacked”Submitted A technical guide to SEO as a story · 239 points
HN discussionThe author seems to forget that ext-based filesystems keep 5% of disk space available for root at all times by default, known as "reserved blocks".[0] That means if a non-root user uses all of the available space, it wasn't really all of the space -- root still has access to 5% free space within that partition. That's exactly the same as the useless 8GB file but in an officially-supported manner. If you run out of d…
Comment linking /change-reserved-blocks-ext3-ext4-filesystem-linux/
on “All my servers have an 8 GB empty file on disk”Submitted Next Chrome Update Will Block SHA-1 Certificates as a story · 199 points
HN discussionOne other option is increasing the reserved block count ( https://ma.ttias.be/change-reserved-blocks-ext3-ext4-filesys... ). This has the nice side effect of increasing the space available for critical daemons. If you haven't customised this, in a pinch you can still lower it down a bit to buy some time.
Comment linking /change-reserved-blocks-ext3-ext4-filesystem-linux/
on “All my servers have an 8 GB empty file on disk”Submitted Chrome to force .dev domains to HTTPS via preloaded HSTS as a story · 193 points
HN discussion248 days of uptime by any chance? edit: I saw the same on a fleet of thousands of JVMs which hung on 100% CPU after 248 days very consistently. Closest thing to an explanation I ever got was perhaps it is storing uptime in hundredths of a second (why not ms???) in signed 32 bit integers, see: https://ma.ttias.be/248-days/ In the end we solved it by restarting with a cronjob between 2am and 4am after 247 days...
Comment linking /248-days/
on “Former Tesla Firmware Engineer Discusses the System”Submitted Google’s QUIC protocol: moving the web from TCP to UDP as a story · 186 points
HN discussionI was excited to see this as just last night I was using FFmpeg to combine digital (legally owned) movies with multiple parts into a single MKV file. It worked great, the one thing (and this is undoubtedly just a knowledge problem on my part), is I could not get it to copy/include subtitles from both parts. I have a feeling I might need to extract the subtitle files and combine them and then re-include the combined…
Comment linking /use-ffmpeg-combine-multiple-videos/
on “FFmpeg by Example”Submitted In 2017, I’m going to stop watching the news as a story · 183 points
HN discussionSelf promotion: https://ma.ttias.be Not daily, but plenty of links to follow-up on. Alternatively, weekly summary of all things Linux & open source (RSS feed available); https://cronweekly.com
Comment linking /
on “Ask HN: What are some good technology blogs to follow?”Submitted I forgot how to manage a server as a story · 166 points
HN discussionRelated to this, I've been following a practice I call "Release Notes Driven Development", which is perfect for side projects. Don't worry too much about technical debt (although, keep it under control), but focus on the little time you have and how to make that as efficient as possible. I wrote about it here; https://ma.ttias.be/release-notes-driven-development-rndd/
Comment linking /release-notes-driven-development-rndd/
on “The art of over-engineering your side projects”Submitted What is a 'unikernel'? as a story · 154 points
HN discussionOne of the random thoughts I had was that I’m sure there’s going to be plenty of clever ways to obfuscate the jndi payload, sort of how you can ping an IP address in octal, an integer, or hex: https://ma.ttias.be/silly-little-ip-tricks/
Comment linking /silly-little-ip-tricks/
on “Log4Shell update: second Log4j vulnerability published”Submitted Magento eCommerce PHP Remote Code Execution as a story · 143 points
HN discussionThis is an excellent example that shows the dangers of terminal escape sequences. Just a shameless plug, but here's a more detailed post (of mine) on the subject: Terminal escape sequences – the new XSS for Linux sysadmins: https://ma.ttias.be/terminal-escape-sequences-the-new-xss-fo...
Comment linking /terminal-escape-sequences-the-new-xss-for-linux-sysadmins/
on “Don't copy paste from a website to a terminal”Submitted There’s more than one way to write an IP address as a story · 140 points
HN discussionAnd remember to use cat -v if you read it with cat. https://ma.ttias.be/terminal-escape-sequences-the-new-xss-fo...
Comment linking /terminal-escape-sequences-the-new-xss-for-linux-sysadmins/
on “Don't copy paste from a website to a terminal”Submitted The text adventure game of exiting a Telnet session as a story · 136 points
HN discussionIf you’re into Laravel and PHP, Freek is very open about all his code: https://freek.dev I also blog about code and the financial side of running your own business: https://ma.ttias.be
Comment linking /
on “Ask HN: What are good solo developer blogs that you enjoy reading?”Submitted Google Chrome 51 disables HTTP/2 on most Linux distros due to old OpenSSL as a story · 132 points
HN discussionReminds me of that classic OSX root login bypass by not using a password from 3 years ago: https://ma.ttias.be/root-login-without-password-allowed-defa...
Comment linking /root-login-without-password-allowed-default-mac-osx-high-sierra/
on “BitLocker Lockscreen Bypass”Submitted Audi Cruise Control Bug as a story · 112 points
HN discussionFor anyone interested in the code behind the halving, I had some fun dissecting the GetBlockSubsidy() function that takes care of halving & ending of block subsidy [1]. It continues to amaze me that I struggle to set up a 5-node database cluster without one going out-of-sync or split-braining every few weeks, yet the bitcoin network manages to keep thousands of miners in-sync. This has to be the best example of even…
Comment linking /dissecting-code-bitcoin-halving/
on “Bitcoin Halving Just Occured”Submitted Double-clicking on the Web as a story · 106 points
HN discussion
