Sudden short-term consumption of resources by Firefox - what could be the reason?

Question

Browsers

For the third or fourth time, I notice how Firefox suddenly starts consuming a huge amount of RAM, causing all programs to slow down. It does not last long: a few minutes; then the system returns to normal.
What can be the reason: a virus in the system, a tab miner, a browser memory leak?
Technical details: Firefox 62.0b10 (64-bit), Windows 7. Adguard ad blocker. Antivirus Comodo Internet Security.

Answer 1

Try searching here:
about:cache?storage=memory&context=
and here:
about:memory
PS Links must be manually copied and pasted into the address bar.