| Blog & site | https://www.michalspacek.com/ |
| Blog & site in Czech | https://www.michalspacek.cz/ |
| Password storage disclosures | https://pulse.michalspacek.cz/passwords/storages |
| Reporting API Demos, CSP etc. | https://canhas.report/ |
| Blog & site | https://www.michalspacek.com/ |
| Blog & site in Czech | https://www.michalspacek.cz/ |
| Password storage disclosures | https://pulse.michalspacek.cz/passwords/storages |
| Reporting API Demos, CSP etc. | https://canhas.report/ |
Here's your (ir)regular reminder that HTTPS certificates without the CN (Common Name) field are completely valid. For example the 6-day certificates from Let's Encrypt do not have a CN as per the "shortlived" profile https://letsencrypt.org/docs/profiles/
Browsers do not use CN for validation even if it exists, they use the SAN (Subject Alternative Name) field only. Baseline Requirements by CA/Browser Forum say that "For Subscriber Certificates, the Subject Alternative Name MUST be present", while the section about Subscriber Certificate Common Name Attribute begins with "If present".

A profile is a collection of characteristics that describe both the validation process required to get a certificate, and the final contents of that certificate. For the vast majority of Let’s Encrypt subscribers, you should never have to worry about this: we automatically select the best profile for you, and ensure that it complies with all of the requirements and best practices that govern the Web PKI. But some people might be interested in proactively selecting a specific profile, so this page exists to provide the information necessary to make that choice.
I always find entering personal details into a company website to tell them to stop processing the very same data a bit absurd.
This business data enrichment company is processing my personal phone number. They told me to fill out this form to opt-out, so I did. Now I'm asking how they process my data I have entered into the form 😅
There's a chance they need to store my data to not use them anymore if a new "enrichment source" appears, sort of a "lock". They also say they're not controllers as per GDPR, only processors, so they can't delete my data, but entering my data could made them one.
I could be wrong though. This will be interesting🤔 And I hope I'll learn a thing or two.
One of my favorite XSS tricks when you can add only attributes (when < and > are removed from the input) is to add onfocus=alert(1) and autofocus: <input value="" onfocus="..." autofocus="">.
To not create a "focus loop", I often add this.blur() to the onfocus handler, otherwise alert(1) steals the focus, and when you close it, the field gains focus once again and so on 😅
Instead of `cat`, I use `bat`, "a cat(1) clone with wings." https://github.com/sharkdp/bat
It supports syntax highlighting, line numbers, git, invisible chars etc. I even have it aliased to `cat`.
But if you'd like to concat multiple files into a single file like `cat 1 2 3 > foo`, you should run the original unaliased `cat` (by prefixing it with `\`, like `\cat`), seems much faster, at least in my case up to 10x. So now my scripts contain `\cat` instead of just `cat`.
Michal Špaček @spazef0rze presenting his talk "Password Reuse Is a Dumpster Fire – We Brought a Hose" at #PasswordsCon in Prague, December 2, 2025.