SharePoint Online - Query String Parameter "p" throws error

[Supun Bulathsinghala]

I got a very weird behavior on couple of days back.

I have a production tenant where I'm using a content search web part to load data dynamically based on the query string parameter value of the page url. I've used "p" as the query string parameter (ex: Search.aspx?p=Alarms) and has been working fine for the last one and half years till now. 

Now when I go to the page with query string parameter "p", page goes to the default error page with "Sorry, something went wrong" message.

Then I tried this in any of the publishing pages, and the result was same. When I append query string parameter "p", the page throws an error. 

I know for a fact, "p" is not a reserved query string param for SharePoint. 

Any idea why this has happened suddenly ? 

Regards,

Supun

[#2]

My guess is "p" recently became a new reserved Query String Parameter. How are you so sure it isn't? I'm not aware of official documentation describing these. I know some blogs describing reserved parameters but those are all quite old....

[#3]

@Supun Bulathsinghala , did you solved this?

I have the same problem in a SP 2019 onpremise site.