That is one of few reasons why mainstream feminism in Korea is radical feminism and not liberal feminism, as issues there very serious and not adressed by government at all for at least 10 years of it happening and increasing.

This problem is similar to japanese problem of women and school girls being groped in public transport. In big cities almost 100% of women were sexually harassed at least once in their lives in public transport. Last 4 years Japan is fighting against it, there were added female-only sections in public transport, for example, and punishment became much more severe. So now it goes down, but not that hugely down, as women still not always believed and they are portrayed as "she just want to ruin that man's life", etc.

Back to Korea. There even separate word for thoss spy cameras: https://en.wikipedia.org/wiki/Molka

And in general - every year it becomes worse and worse, in 2019 and 2020 those cameras started appearing in female-only spaces too, previously they were mainly in unisex spaces, so it was almost impossible to use unisex spaces without a fear to then appear on porn sites or sold for perverts on usb-flash sticks (and porn is illegal in Korea): https://www.bbc.com/news/world-asia-50582338

https://www.japantimes.co.jp/news/2020/01/13/asia-pacific/crime-legal-asia-pacific/south-korea-spy-cam-epidemic/

That's really huge problem there.

I know it is an issue in USA and Canada as well, but it is not very common and mostly appears only in unisex toilets, and mostly where younger women/girls are visiting them. So in school, colleges, universities, sports circles.

In UK in unisex bathrooms/toilets in sports circles rape cases are 9 times more often occuring than in sports circles with single-sex bathrooms/toilets. Sexual harassment and body shaming or period shaming happens 80+ times more often in unisex ones. And UK is one of safest countries with least of offenses in the world. So in other countries this number should be much worse.