‘/l/’ in a URL of unknown origin

I have a strange issue with my project. After analyzing the log files, I noticed that in one of the categories, when using filters, a weird URL appears. The typical URL looks like this: /data.html?data_lg=6+m. However, somewhere in the project, there seems to be a redirect that leads to URLs like /data/l/6-m.html. I have searched through the source code, but I can’t find the location of this redirect or anything related.