On: You are dangerously bad at cryptography

[pcwalton]

Memory safety in memory-unsafe languages. We've had Valgrind and ASan for a while, and people still find crippling bugs in C and C++ code all the time.

XSS vulnerabilities. Maybe Content Security Policy will help some here when it becomes ubiquitously available.

Integer overflow. This is a particularly insidious problem because your well-formed test cases often won't catch it.

[jimmaswell → pcwalton]

Here's a gem from an attempt to fix an integer overflow vulnerability in the PHP compiler:

if (size > INT_MAX) return NULL;

http://use.perl.org/use.perl.org/_Aristotle/journal/33448.ht...