In MediaWiki through 1.37, XSS can occur in Wikibase because an external identifier property can have a URL format that includes a $1 formatter substitution marker, and the javascript: URL scheme (among others) can be used.
MediaWiki before 1.36.2 allows a denial of service (resource consumption because of lengthy query processing time). ApiQueryBacklinks (action=query&list=backlinks) can cause a full table scan.
MediaWiki before 1.36.2 allows a denial of service (resource consumption because of lengthy query processing time). Visiting Special:Contributions can sometimes result in a long running SQL query because PoolCounter protection is mishandled.
An issue was discovered in MediaWiki through 1.36.2. A parser function related to loop control allowed for an infinite loop (and php-fpm hang) within the Loops extension because egLoopsCountLimit is mishandled. This could lead to memory exhaustion.
An issue was discovered in CentralAuth in MediaWiki through 1.36.2. The rightsnone MediaWiki message was not being properly sanitized and allowed for the injection and execution of HTML and JavaScript via the setchange log.
An issue was discovered in SpecialEditGrowthConfig in the GrowthExperiments extension in MediaWiki through 1.36.2. The growthexperiments-edit-config-error-invalid-title MediaWiki message was not being properly sanitized and allowed for the injection and execution of HTML and JavaScript.
An issue was discovered in Special:MediaSearch in the MediaSearch extension in MediaWiki through 1.36.2. The suggestion text (a parameter to mediasearch-did-you-mean) was not being properly sanitized and allowed for the injection and execution of HTML and JavaScript via the intitle: search operator within the query.
An issue was discovered in the Mentor dashboard in the GrowthExperiments extension in MediaWiki through 1.36.2. The Growthexperiments-mentor-dashboard-mentee-overview-add-filter-total-edits-headline, growthexperiments-mentor-dashboard-mentee-overview-add-filter-starred-headline, growthexperiments-mentor-dashboard-mentee-overview-info-text, growthexperiments-mentor-dashboard-mentee-overview-info-legend-headline, and growthexperiments-mentor-dashboard-mentee-overview-active-ago MediaWiki messages were not being properly sanitized and allowed for the injection and execution of HTML and JavaScript.