Judging from a Facebook page for a University of Calgary event, you might think thousands of students are interested in a Nazi-themed protest of Justin Trudeau — but Nina Rojkovskaia wants you to know that's not how the page looked when she initially responded.

The U of C student said she and her friends appear to have fallen victim to a bait-and-switch. The page was initially set up last week to look like an event listing for the prime minister's town hall at the university on Tuesday night.

But the title and description of the event were altered the day before Trudeau's visit, and the posts on the page veered from questions about how to attend the town hall into anti-Jewish rhetoric.

An internet security expert says the page may have been sold to a third party and that Facebook could decide to take it down — but only if enough people complain.

Some of the anti-Semitic comments came from Facebook profiles that include images of Nazi flags and people with parentheses around their heads, a relatively new online signal targeting Jews that has been added to the Anti-Defamation League's hate symbol database.

Rojkovskaia said she was troubled by the change as she and some 1,500 other people had already RSVP'd to the event and another 3,400 had indicated — publicly, for anyone who visits the page to see — that they were interested.

"I'm definitely not wanting to be associated with that," Rojkovskaia said.

"I'm really concerned ... about that being misrepresented as student support."

Profiles that posted to the University of Calgary "event" page with hate symbols in their cover photos. CBC has removed one obscene word from the screenshot at left. (Facebook/Screenshot)

​The number of people listed as interested or going to the event fell by 1,500 after the page title was changed, but Rojkovskaia said she's concerned many people who RSVP'd last week may not have checked the page recently and may unwittingly end up attending a protest they don't agree with.

"I think that's just highly dishonest," she said.

"If a group of protesters want to gather support for their cause, they should do it in a more honest way."

Ryan Lacroix, who's not a U of C student but was interested in attending the prime minister's town hall, said he RSVP'd to the Facebook event last week and then didn't look at it again until Monday.

"It was very different from what it was when I first looked at it," he said.

"It changed dramatically from what it was to what it is now."

The top image shows how a Facebook event for "Justin Trudeau - U of C visit" appeared as of noon on Monday, as accessed via Google cache. The bottom image is how the event appeared Tuesday morning, having been altered to "Justin Trudeau - U of C Protest." (Google cache/Facebook/Screenshots)

Rojkovskaia said she was blocked from accessing the event page after calling the administrators out.

CBC News contacted someone listed as an administrator for the page by email, who replied that the event "was always a protest group."

But Google cache, which archives past versions of websites, shows the event page as being titled "Justin Trudeau - U of C visit" with a photo of the prime minister in front of a Canadian flag as of noon on Monday.

It was later changed to "Justin Trudeau - U of C Protest" and a photo of Trudeau with Fidel Castro.

And while early posts on the page discussed how to attend Trudeau's visit and debated the prime minister's policies, later posts veered into anti-Jewish rhetoric, anti-immigrant memes, and a vulgar sexual reference about the prime minister's wife.

The administrators of the page changed several times, but it's unclear who is actually behind it. The administrator profiles contain limited or fake information.

A post on another event-listing website appeared to offer the initial "Justin Trudeau – U of C visit" Facebook event for sale.

"If someone wants to take over this event and pay me for it, email me," the post reads.

Page may have been bought and sold

Computer security expert Tom Keenan said it's not unheard of for people to sell Facebook events, sometimes along with entire Facebook profiles and email accounts.

"You're not supposed to sell Facebook pages — it's against the terms of Facebook — but people do it and, once somebody has possession of the page, they can put whatever they want up there until somebody gets around to complaining about it," he said.

Keenan said he wouldn't be surprised if Facebook took the event listing down, as the company has "absolute discretion" over what appears on the site.

"If they decide something brings Facebook or anybody on it into disrepute, they can take it down," he said.

"Then again they may just say, 'Hey, that's Canada. We don't care.'"

In general, Keenan advised taking unofficial listings for public events "with grains of salt" and said to be aware that the internet is full of deceptive people.

"There's plenty of fake of stuff out there, so this is just one more fake thing," he said.

Prime Minister Justin Trudeau passes by reporters as he arrives at a Liberal cabinet retreat in Calgary, Alta., on Tuesday, Jan. 24, 2017. He is set to hold a town hall at the University of Calgary on Tuesday evening. (Jeff McIntosh/The Canadian Press)

The prime minister's actual town hall at the University of Calgary is set to start at 7 p.m. on Tuesday in the Jack Simpson Gymnasium.

Calgary Centre Liberal MP Kent Hehr said everyone is welcome to attend, whether they support or oppose the prime minister, but the event is expected to be filled to capacity.

"This evening I look forward to joining Prime Minister Trudeau at the University of Calgary for an engaging discussion with Canadians," Hehr said in an email.

"This will be a great opportunity to hear from Calgarians of all ages and political stripes and discuss the issues that matter most to them."