Escaped Defect
An escaped defect is a defect that was not detected during testing and is discovered after the software has been released or delivered to users.
“A defect that was not detected by a testing activity that is supposed to find that defect.”
(Definition reproduced from the ISTQB Glossary. Copyright belongs to ISTQB.)
View the complete ISTQB GlossaryWhat is Escaped Defect?
Escaped defects indicate that existing testing activities failed to identify a problem before release. They are often analyzed to improve future testing processes.
Post-release discovery: Customers or production monitoring identify the defect.
Quality indicator: A high number of escaped defects may indicate weaknesses in testing.
Continuous improvement: Root cause analysis helps reduce future escapes.
Real World Example
A hospital medication system shows a different dosage warning in test than the one specified by the clinical safety rule.
The team needs precise language to separate what was observed, what should have happened, and whether the difference represents a reportable issue. Escaped defect provides that distinction.
The tester records the steps, data, observed behavior, expected behavior, and evidence so triage can focus on patient safety impact instead of vague descriptions.
The issue is handled faster because Escaped defect helps everyone discuss the problem using a shared testing vocabulary.
Practice Questions
Question 1
Which statement BEST describes Escaped defect in the context of ISTQB terminology?
Question 2
A tester needs to explain Escaped defect to a non‑technical stakeholder. Which approach is MOST appropriate?
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