diff --git a/modules/markup/asciicast/asciicast.go b/modules/markup/asciicast/asciicast.go
index 0678062340..873029c1bd 100644
--- a/modules/markup/asciicast/asciicast.go
+++ b/modules/markup/asciicast/asciicast.go
@@ -39,7 +39,7 @@ const (
 // SanitizerRules implements markup.Renderer
 func (Renderer) SanitizerRules() []setting.MarkupSanitizerRule {
 	return []setting.MarkupSanitizerRule{
-		{Element: "div", AllowAttr: "class", Regexp: regexp.MustCompile(playerClassName)},
+		{Element: "div", AllowAttr: "class", Regexp: regexp.MustCompile("^" + playerClassName + "$")},
 		{Element: "div", AllowAttr: playerSrcAttr},
 	}
 }
diff --git a/modules/markup/csv/csv.go b/modules/markup/csv/csv.go
index 1dd26eb8ac..c700fb8dfc 100644
--- a/modules/markup/csv/csv.go
+++ b/modules/markup/csv/csv.go
@@ -37,9 +37,9 @@ func (Renderer) Extensions() []string {
 // SanitizerRules implements markup.Renderer
 func (Renderer) SanitizerRules() []setting.MarkupSanitizerRule {
 	return []setting.MarkupSanitizerRule{
-		{Element: "table", AllowAttr: "class", Regexp: regexp.MustCompile(`data-table`)},
-		{Element: "th", AllowAttr: "class", Regexp: regexp.MustCompile(`line-num`)},
-		{Element: "td", AllowAttr: "class", Regexp: regexp.MustCompile(`line-num`)},
+		{Element: "table", AllowAttr: "class", Regexp: regexp.MustCompile(`^data-table$`)},
+		{Element: "th", AllowAttr: "class", Regexp: regexp.MustCompile(`^line-num$`)},
+		{Element: "td", AllowAttr: "class", Regexp: regexp.MustCompile(`^line-num$`)},
 	}
 }
 
diff --git a/modules/markup/sanitizer_default.go b/modules/markup/sanitizer_default.go
index 669dc24eae..1f989b54c1 100644
--- a/modules/markup/sanitizer_default.go
+++ b/modules/markup/sanitizer_default.go
@@ -67,10 +67,10 @@ func (st *Sanitizer) createDefaultPolicy() *bluemonday.Policy {
 	}
 
 	// Allow classes for anchors
-	policy.AllowAttrs("class").Matching(regexp.MustCompile(`ref-issue( ref-external-issue)?`)).OnElements("a")
+	policy.AllowAttrs("class").Matching(regexp.MustCompile(`^ref-issue( ref-external-issue)?$`)).OnElements("a")
 
 	// Allow classes for task lists
-	policy.AllowAttrs("class").Matching(regexp.MustCompile(`task-list-item`)).OnElements("li")
+	policy.AllowAttrs("class").Matching(regexp.MustCompile(`^task-list-item$`)).OnElements("li")
 
 	// Allow classes for org mode list item status.
 	policy.AllowAttrs("class").Matching(regexp.MustCompile(`^(unchecked|checked|indeterminate)$`)).OnElements("li")
@@ -79,7 +79,7 @@ func (st *Sanitizer) createDefaultPolicy() *bluemonday.Policy {
 	policy.AllowAttrs("class").Matching(regexp.MustCompile(`^icon(\s+[\p{L}\p{N}_-]+)+$`)).OnElements("i")
 
 	// Allow classes for emojis
-	policy.AllowAttrs("class").Matching(regexp.MustCompile(`emoji`)).OnElements("img")
+	policy.AllowAttrs("class").Matching(regexp.MustCompile(`^emoji$`)).OnElements("img")
 
 	// Allow icons, emojis, chroma syntax and keyword markup on span
 	policy.AllowAttrs("class").Matching(regexp.MustCompile(`^((icon(\s+[\p{L}\p{N}_-]+)+)|(emoji)|(language-math display)|(language-math inline))$|^([a-z][a-z0-9]{0,2})$|^` + keywordClass + `$`)).OnElements("span")