DoubleVerify, which builds software for digital media advertisers, closed up 33% on its first day of trading after its IPO, giving it a market cap of $5.3B+ (Megan Graham/CNBC)

Megan Graham / CNBC:
DoubleVerify, which builds software for digital media advertisers, closed up 33% on its first day of trading after its IPO, giving it a market cap of $5.3B+  —  - DoubleVerify, a company that builds software for digital media, began trading Wednesday.  — It attempts to help advertisers …