Potentially Unwanted Programmes as Firefox Extension.
Malware and Adware scanning fetched two results and they are associated with Mozilla Firefox. I attach two screenshots. Please solve the problem.
Remove those and find replacements.
You may have ad/mal-ware. Further information can be found in this article; https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware?cache=no
Run most or all of the listed malware scanners. Each works differently. If one program misses something, another may pick it up.