Headteachers are being urged to remind their students about the dangers of sharing exam questions on social media.
Exam regulator Ofqual has today published a letter, written by chief regulator Sally Collier, advising heads on potential risks to the smooth delivery of the exams taken this year.
Coronavirus: Ofqual braces for exam disruption risk
Investigation: More pupils experiencing ‘dark thoughts’ about exams
Ms Collier urged school leaders to ensure students understand the consequences of sharing papers or questions online, regardless of whether the content turns out to be "real or fake".
She said: "We know that students often take to social media after their exams to voice their views about exam papers, but there have been instances, before exams take place, of individuals claiming to have copies of live questions or papers, and in some cases offering them for sale.
"I urge you to remind your students not to be distracted by such claims, or to share them. Sharing exam papers or questions, real or fake, could result in disqualification."
Ms Collier added that, if either teachers or students have any reason to believe the security of an exam paper has been compromised, they should inform the relevant exam board "immediately".
Ofqual also used today's letter to warn heads that some students still "do not understand" the consequences of taking mobile phones into exams.
"We know that exams officers put a lot of work into getting this message across, but still some students do not understand the possible consequences of breaching this rule," Ms Collier said.