Thousands of A-Level students have had their exams plunged into chaos after a spate of online leaks linked to Pakistan.
Leading exam board Cambridge International has voided physics papers that were sat last week after it emerged the questions had been 'shared prematurely'.
Pupils will instead be assigned a mark based on their performance in other modules.
It is the latest in a series of leaks leaving university hopefuls worried they may not achieve the grades they need to get in.
Exam material has been 'circulated' in Pakistan, according to the board, and local media reported that a national cyber crime investigation has been opened.
Earlier this month, the board also confirmed that an AS and A-level maths papers had been leaked – as well as an AS computer science exam.
Online platforms such as Reddit and Discord have been flooded with images purporting to be from this year's papers – some of which appear to be genuine.
Tobias Eatough told the Daily Mail: 'From what I've seen, pretty much every single exam has been leaked.
Leading exam board Cambridge International has voided physics papers that were sat last week after it emerged the questions had been 'shared prematurely'
'A couple of hours before, you get at least five people posting... And from there, it spreads.'
Tobias, 18, is sitting A-levels in maths, physics and biology and was confident that he would secure the three As needed to study medical biosciences at Imperial College London. But he must now retake two exams because of the leaks and is struggling to recap the content alongside his other subjects.
'One of the papers that I felt went best has been cancelled, and they're now going to assign me a mark, which is just completely unfair,' he said.
'It feels like something that should be in my control, but it's completely out of my hands now. You do so much revision and you're not even sure if it will count.'
Cambridge's qualifications are taken by pupils at almost 5,000 schools in 138 countries – including some independent schools in the UK.
Declaring last Wednesday's physics AS and A-level papers void, Cambridge said that pupils who took it – including in the UK, Europe and the Middle East – will now be given an 'assessed mark'.
To do this, the board creates a ranking of all the pupils in the world who take the same combination of modules.
Based on what they achieve in their other exams, they are awarded a corresponding mark for the one they did not sit.
A second physics paper due to be taken tomorrow has also been replaced.
Another pupil from London, studying maths, computer science and economics, told the Daily Mail he was concerned about retakes scheduled for June.
He said: 'I thought I had two weeks between my last exams and my next economics one. Now I have to revise all of that content at the same time - and these are hefty papers worth about 60 per cent of my grades.
He hopes to study law and has had offers from five Russell Group universities, but said the leaks have put 'a lot of pressure' on him.
'When I don't want to stress myself out on the morning of an exam, sometimes I just scroll on Instagram, and then I might see a paper. It's just how it is now - you don't even have to look it up,' he said.
In a statement earlier this month, Cambridge said its AS computer science exam had been 'shared prematurely in Pakistan', but that this did not necessarily mean the leak originated there.
According to local media, the board has been in contact with the country's National Cyber Crime Investigation Agency.
Sam Gower, a maths teacher from Britain, has started an online petition, demanding, among other things, a guarantee that university places will not be affected by any potentially delayed retake grades.
A spokesman for Cambridge International said: 'We have acted swiftly to put alternative measures in place for impacted students. It remains rare for the integrity of an exam to be compromised
'The theft of these papers is the subject of an active investigation, and we are working closely with relevant law enforcement authorities and other partners.'