https://www.pbs.org/newshour/politics/who-is-alvin-bragg-the-manhattan-district-attorney-overseeing-case-against-trump
Alvin Bragg became Manhattan’s first Black district attorney in 2022, following his election in November 2021. Bragg inherited a years long grand jury investigation into hush money paid on Trump’s behalf during his 2016 presidential campaign, Bragg convened a new grand jury early this year.
https://www.britannica.com/biography/George-Soros
George Soros, Hungarian-born American financier, author, philanthropist, and activist whose success as an investor made him one of the wealthiest men in the world. He was also known as a powerful and influential supporter of liberal social causes. He is known as a Democratic "megadonor"
https://www.nytimes.com/2023/03/23/us/politics/alvin-bragg-george-soros-trump.html
Mr. Bragg announced his candidacy for the position in June 2019. Nearly two years later, on May 8, 2021, the political arm of Color of Change, a progressive criminal justice group, endorsed him. It pledged to spend $1 million on direct mailers, on-the-ground campaigning and voter turnout efforts on his behalf. (It did not donate to Mr. Bragg’s campaign directly.) A few days later, on May 14, Mr. Soros contributed $1 million to the group, which intended to help Mr. Bragg with the money. Mr. Soros was just one of many large donors to the group.
So yes, Alvin Bragg's campaign for DA was financially supported by George Soros through the Color of Change group.
is it illegal:
Color of Change is a 501(c)(4) advocacy organizing with an affiliated political action committee. Meaning Color of Change follows PAC rules for financial support
https://www.fec.gov/help-candidates-and-committees/making-disbursements-ssf-or-connected-organization/limits-contributions-made-candidates-by-ssf/
I looked here and found that the maximum amount that an individual can contribute to a candidate for federal office is $2,900 per election, and the maximum amount that an individual can contribute to a national party committee is $35,500 per year. It is possible that the donation by Color of Change exceeded the limits set by the FEC, which could be a violation of campaign finance laws. However, it's also possible that the donation was made to a separate organization, such as a super PAC, which can raise and spend unlimited amounts of money to support political candidates as long as they do not coordinate their activities with the candidate's campaign.
I also found that receiving a donation from George Soros or any other individual or organization is not illegal in and of itself, it's the campaign finance laws that limit the amount of money that can be contributed and require transparent donations.