A major security vulnerability
in India's income tax filing portal has been fixed, TechCrunch reported. The flaw, discovered
by security researchers Akshay CS and "Viral" in September, allowed
logged-in users to access real-time personal and financial information of other
taxpayers. This included sensitive details such as full names, home addresses,
email addresses, dates of birth, phone numbers and bank account information.
Exposed Aadhaar numbers of
individuals
The security flaw in the income
tax filing portal also exposed Aadhaar numbers, a unique government-issued
identification number used for identity verification and accessing government
services. TechCrunch verified the data by allowing researchers to search
its records on the portal. The researchers confirmed on October 2 that the
vulnerability had been patched. Discovery process
Researchers found bug while
filing tax returns
The researchers found the
security flaw while filing their recent income tax return on the government website. They discovered that by logging
into the portal with their Permanent Account Number (PAN), they could view
anyone else's sensitive financial data by replacing their PAN with another in a
network request as the page loads. This could be done using publicly available
tools like Postman or Burp Suite and knowledge of someone else's PAN. Exploitation
details
Vulnerability was easily
exploitable by anyone logged into tax portal
The vulnerability was
exploitable by anyone logged into the tax portal because the Income Tax
Department's back-end servers were not properly checking who could access a
person's sensitive data. This type of vulnerability is known as an insecure
direct object reference (IDOR), a common flaw that governments have warned can
be easily exploited and lead to large-scale data breaches.
Bug also exposed data of
individuals who didn't file taxes
Along with individual data, the
bug also exposed information related to companies registered with the e-Filing
portal. TechCrunch verified that the bug even exposed data of
individuals who had not filed their income tax returns for the current year.
This was confirmed by asking an individual yet to file their tax returns for
permission to let researchers look up their information using this portal bug.