Yes, all tax-exempt organizations in the US are required to publish a copy of IRS Form 990. This includes a breakdown of income, expenses (including executive compensation), and assets.

The Wikimedia Foundation also publishes audited financial statements and a plan for the coming year. All of this is available here [1], which is the first result when you Google "wikipedia financials".

[1] https://wikimediafoundation.org/about/financial-reports/