New and better tools are finding bugs in old code, so it isn't really that more and more bugs get into new code:
"But, your editor wondered, could we be doing more than we are? The response your editor got was, in essence, that the bulk of the holes being disclosed were ancient vulnerabilities which were being discovered by new static analysis tools. In other words, we are fixing security problems faster than we are creating them. "
"But, your editor wondered, could we be doing more than we are? The response your editor got was, in essence, that the bulk of the holes being disclosed were ancient vulnerabilities which were being discovered by new static analysis tools. In other words, we are fixing security problems faster than we are creating them. "
https://lwn.net/Articles/410606/