Escaped defect
An escaped defect is a bug that passes every check before release (review, tests, staging) and is found in production, by monitoring, support tickets or customers.
Why it matters
Counting escaped defects is how teams measure whether their checks work, because a bug caught in review costs a comment while a bug caught in production costs an incident, a fix under pressure and sometimes data that cannot be repaired. Each stage catches some bugs and lets others through, and the escapes are the bugs no stage was looking for.
Code review is the one stage that reads the change with the requirements in mind, so it is the stage that catches what tests were never written for: a missing timeout, a wrong field in a total, an ownership check nobody thought to test. Looking back at an escaped defect usually shows a diff where the problem was visible, and a review that did not stop on that line.
See also
- Review recall
- Rubber-stamping
- Worked example: requests.get with no timeout can hang the handler forever in Python, a missing timeout that only bites when the upstream is slow