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security/sql-injection-how-a-quote-mark-in-a-login-form-can-rewrite-the-databas.md SQL injection: how a quote mark in a login form can rewrite the database's question A login form builds a database question out of the words you type. If it glues your text straight into the question, your text can rewrite… 5 min read · 21 Oct computer-science/big-o-how-to-tell-if-your-code-will-survive-1-000-times-more-data.md Big O: how to tell if your code will survive 1,000 times more data Your code works on 10 items, then crawls on 10,000. Big O is the short way programmers describe how the number of steps grows as the input… 4 min read · 11 Oct security/two-factor-codes-how-your-phone-and-a-website-agree-on-6-digits.md Two-factor codes: how your phone and a website agree on 6 digits Your phone shows a 6-digit code that changes every 30 seconds, yet it never talks to the website. How do both sides agree on the number?… 5 min read · 9 Oct software-design/pure-functions-why-the-same-call-can-give-two-different-answers.md Pure functions: why the same call can give two different answers Call a function twice with the same input and get two different answers? Python isn't broken. The function is doing something extra, called… 5 min read · 9 Oct security/sql-injection-how-a-stray-quote-mark-turns-data-into-instructions.md SQL injection: how a stray quote mark turns data into instructions A search box looks harmless, but if a program builds its database question by gluing text together, a stray quote mark can turn a visitor's… 4 min read · 6 Oct software-design/your-first-unit-test-catch-the-leap-year-bug-a-quick-check-misses.md Your first unit test: catch the leap-year bug a quick check misses A unit test is a tiny piece of code that checks another piece of code: you pick an input, write down the answer you expect, and let the… 5 min read · 3 Oct