As noted elsewhere, this show has a habit of updating and re-releasing episodes months - or more often years - after their original airing. However, the way these episodes are presented on PBS websites has changed. They used to list both the original episode and the updated episode, with their respective airdates. Now they list the updated version in place of the original version (i.e., with the original's season#, episode#, and airdate), and usually include the original episode as an "extra" within it.

This is true for:

• 2003-01-09 "A Dangerous Business" >> 2008-02-05 "A Dangerous Business Revisited" (original episode not included)
• 2011-09-06 "Top Secret America" >> 2013-04-30 "Top Secret America: 9/11 to the Boston Bombings"
• 2012-11-20 "Poor Kids" >> 2017-11-22 "Poor Kids"
• 2019-05-21 "Supreme Revenge" >> 2020-11-24 "Supreme Revenge: Battle for the Court"

For clarity, I'm looking at both the PBS main site and the WGBH program site.

Exceptions and oddities:

• "A Dangerous Business Revisited" does not include the original episode "A Dangerous Business"
• Neither version of "Top Secret America" is listed in the episode index of the WGBH program site, but an episode page exists and can be found in a Google search
• Listing the updated version of "Top Secret America", which talks about the 2013 Boston Marathon bombings, as being from 2011 (as the PBS main site does), is utterly baffling

I think this approach violates the basic integrity of episode guides, and carries a risk of episodes falling (or being pushed) into the "memory hole".

1999-04-13 "The Terrorist and the Superpower" >> 2000-03-21 "Hunting Bin Laden" >> 2001-09-13 "Hunting Bin Laden" (with introduction by Bill Moyers and possibly other updates)