An Indian school exam board has admitted flaws in its online grading system's cybersecurity, which has impacted thousands of pupils and added to a series of challenges facing the education department of the country.

The government-run Central Board of Secondary Education (CBSE) in a post on X said it has been “closely monitoring” weaknesses in the OnMark portal after a teenager, who identified himself as an "ethical hacker," revealed flaws in the system.

It was the latest issue to affect India’s education sector amid intensified calls for the education minister to resign following the high-profile cancellation of a national exam for medical students.

Last month, thousands of students reported discrepancies in their marks on school-leaving exams, which were allegedly linked to the OnMark portal. The portal, introduced this year, is a digital evaluation system that scans physical answer sheets and uploads them online for assessment by teachers.

Around 1.8 million students took the school-leaving exams in 2026, the results of which were announced on 13 May.

The row ensued after students claimed that the physical answer sheets they received differed from the digital copies provided by the education board as part of the re-evaluation process.

The controversy worsened after Nisarga Adhikary, a teen cybersecurity researcher, claimed the portal could have permitted a full takeover of an examiner’s account and potentially allowed tampering with marks. He said he disclosed five critical vulnerabilities in the marking portal to the country’s computer emergency response team on 25 February.

"We have been closely monitoring the vulnerabilities in the OnMark portal of our service provider that are being flagged in the public domain," the CBSE said in a statement. "The identified vulnerabilities have been contained, and other exploitable weaknesses are being ruled out.

"We are grateful to all alert citizens and ethical hackers pointing out such weaknesses, and have gotten in touch with some of them directly," it added.

The board had earlier denied any connection between the portal’s cybersecurity and the issue with students receiving the wrong marks, arguing that "no security breaches have come to light on the portal deployed for the actual evaluation work".

More than 400,000 students had applied for scanned copies of their answer sheets, while nearly 1.1 million had requested access to the physical scripts, according to reports.

Federal education minister Dharmendra Pradhan last week said strict action will be taken against anyone found intentionally responsible for irregularities affecting students. He added: "This was the first time CBSE used [the OSM process], and some discrepancies have come to light. I take responsibility for this and assure you that a solution will be found. We are working on it. We will not leave any student’s query unaddressed."

Opposition leader Rahul Gandhi has accused prime minister Narendra Modi and his government of presiding over a growing crisis of confidence in the country's education department.

He has demanded the education minister's resignation over the controversies and called for a court-led inquiry into the award of the contract to the external agency responsible for operating and maintaining the grading portal.

Mr Pradhan is also facing mounting criticism after the cancellation of a national medical college entrance test following an alleged question paper leak that affected 2.3 million aspiring doctors.

He said the Modi government was taking extensive measures to conduct a rerun of the exam, scheduled for 21 June, including the use of Indian Air Force aircraft to safely transport the question papers to avoid further leaks.

"The postal department usually uses normal transportation routes. This time, considering security concerns and the need for timely delivery, we requested the Indian Air Force to assist in the secure transportation of question papers," he told NDTV.