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Reporting bad regex for a cool $10k #cybersecurity #bugbounty #developer #computerscience #javascrip
Introduction
A recent security vulnerability discovered by a researcher earned them a ten-thousand-dollar reward from Facebook. The issue stemmed from a flaw in Facebook's URL validation process, which relied heavily on regular expressions (regex) for pattern matching.
The purpose of the regex was to ensure that incoming URLs were properly owned by Facebook. However, a critical oversight occurred when the developers omitted two essential characters: the forward slash (/) and the dot (.). This small mistake allowed malicious URLs—which did not actually belong to Facebook—to bypass the validation checks, leading to an account takeover vulnerability.
The challenge with identifying such issues is that they can be quite subtle and difficult for developers to recognize. Standard security tools often fail to catch these nuanced mistakes, primarily because they do not fully understand the developer's intent.
To mitigate these types of vulnerabilities, a recommended approach is to consolidate security-sensitive operations into a shared library. This strategy would help developers avoid reinventing the wheel and making similar oversights repeatedly.
Until more robust solutions are widely adopted, bug bounty researchers remain vigilant, ready to report such vulnerabilities and reap their rewards.
Keyword
- regex
- pattern matching
- URL validation
- vulnerability
- account takeover
- security tools
- shared library
- bug bounty
FAQ
Q: What is regex?
A: Regex, or regular expressions, is a tool used in programming for pattern matching and text manipulation.
Q: What was the vulnerability discovered in Facebook?
A: The vulnerability was related to incorrect URL validation due to missing characters in the regex, which allowed for potential account takeovers.
Q: How do security tools relate to the vulnerability?
A: Many security tools may not detect these kinds of subtle mistakes because they do not understand the intended behavior of the code.
Q: What can developers do to avoid making similar mistakes?
A: Developers can place security-sensitive functions into shared libraries to ensure consistent implementation and reduce the risk of oversight.
Q: What is a bug bounty?
A: A bug bounty is a reward offered to individuals who identify and report vulnerabilities in software, incentivizing them to improve security.