I didn't know about the salary, what country is that? I'm curious

In Sweden, any document touched by the government is by default open to the public, as an anti-corruption, pro-democracy measure.

Of course, your tax forms are documents touched by the government, in which your declared income is stated.

Norway is one such country (https://www.bbc.com/news/magazine-40669239) but I think some others in the Nordics also does the same, not sure exactly which though and Google is not being very helpful this evening.

It's not exactly true that your salary is public -- what's public is your taxable income, taxable wealth, total estimated tax, birth year and postal code. Various deductions apply to the income which makes it non-straightforward to deduce a person's actual income, and as for taxable wealth the minimums are high enough and deductions are substantial enough (especially if you own a home) that a lot of people with wealth much greater than zero will be listed with a taxable wealth as zero.