"I'm already missing a heartbeat," tweeted Tara Sepehri Far, a researcher working for Human Rights Watch (HRW), as she posted a picture from the St. Petersburg Stadium.
Iran bans women from attending men's sporting events. Breaking the rules could result in arrest, fines or even imprisonment.
"We are so proud of the girls today who are willing to openly take the risks that we wouldn't, but they shouldn't have to face any consequences for such a natural act," wrote Iranian journalist Yeganeh Rezaian -- who lives in the US -- in the Washington Post earlier this week.
HRW has criticized the ban, which also runs counter to the FIFA statues, which prohibit gender discrimination. Article Four says discrimination of any kind is "punishable by suspension or expulsion."
In March, FIFA President Gianni Infantino was criticized by HRW after he attended a top-level football match in Iran.
"When Mr. Infantino was enjoying a football match in men-only stadium, Iranian female football fans were under arrest," wrote At OpenStadiums, an Iranian women's advocacy group on Twitter.
In a statement sent to CNN, football's world governing body said Infantino had been reassured by Iranian President Hassan Rouhani during that March visit that the ban on women would eventually be lifted, though no time was provided.
"FIFA was very concerned to learn about the deeply regrettable incidents of women who attempted to have their voices heard on the subject of women's access to stadia during President Infantino's visit and FIFA raised this issue with the Iranian authorities," the statement said.
"FIFA is fully committed to upholding human rights in accordance with FIFA's Human Rights Policy, including in relation to discriminatory practices.
"While we consider the commitment by the Iranian authorities to be an important step, we are aware that its implementation requires sustained efforts."
If Sepehri missed a heartbeat at the prospect of watching Iran on Friday, she probably missed a few more as the team won their first World Cup game in 20 years thanks to Aziz Bouhaddouz's 95th-minute own goal.
The Iranian Football Federation did not immediately responded to CNN's request for comment.
CNN also asked Iran's team press officer if the team welcomed the support of both men and women in the stadium, but he wasn't immediately available for comment.
Iran are currently playing in their fifth World Cup and, under Portuguese coach Carlos Queiroz, have qualified for two consecutive World Cups for the time in their history.
Queiroz, previously assistant manager to Alex Ferguson at Manchester United, took over "Team Melli" in 2011 after leaving his position as Portugal head coach the previous year.
In St. Petersburg, Iran had goalkeeper Alireza Beiranvand to thank for keeping his team in the game.
Then totally against the run of play and with just seconds remaining, Morocco forward Bouhaddouz inadvertently headed an Iran corner past his own goalkeeper.
The own goal sparked jubilant scenes on the pitch and among the Iranian fans in the stands.
Morocco, meanwhile, will be sorely disappointed to have not capitalized on their dominance and will regret their profligacy in front of goal.