diff --git a/modules/base/markdown.go b/modules/base/markdown.go
index 0ef379b8e..62db945a5 100644
--- a/modules/base/markdown.go
+++ b/modules/base/markdown.go
@@ -29,16 +29,10 @@ func isalnum(c byte) bool {
 	return (c >= '0' && c <= '9') || isletter(c)
 }
 
-var validLinks = [][]byte{[]byte("http://"), []byte("https://"), []byte("ftp://"), []byte("mailto://")}
+var validLinksPattern = regexp.MustCompile(`^[a-z][\w-]+://`)
 
 func isLink(link []byte) bool {
-	for _, prefix := range validLinks {
-		if len(link) > len(prefix) && bytes.Equal(bytes.ToLower(link[:len(prefix)]), prefix) && isalnum(link[len(prefix)]) {
-			return true
-		}
-	}
-
-	return false
+	return validLinksPattern.Match(link)
 }
 
 func IsMarkdownFile(name string) bool {
@@ -346,7 +340,7 @@ OUTER_LOOP:
 func RenderMarkdown(rawBytes []byte, urlPrefix string, metas map[string]string) []byte {
 	result := RenderRawMarkdown(rawBytes, urlPrefix)
 	result = PostProcessMarkdown(result, urlPrefix, metas)
-	result = Sanitizer.SanitizeBytes(result)
+	result = BuildSanitizer().SanitizeBytes(result)
 	return result
 }
 
diff --git a/modules/base/tool.go b/modules/base/tool.go
index f98ae28b9..5280fef20 100644
--- a/modules/base/tool.go
+++ b/modules/base/tool.go
@@ -37,6 +37,7 @@ func BuildSanitizer() (p *bluemonday.Policy) {
 
 	p.AllowAttrs("type").Matching(regexp.MustCompile(`^checkbox$`)).OnElements("input")
 	p.AllowAttrs("checked", "disabled").OnElements("input")
+	p.AllowURLSchemes(setting.Markdown.CustomURLSchemes...)
 	return p
 }
 
diff --git a/modules/setting/setting.go b/modules/setting/setting.go
index fcb234add..1ef20fd3c 100644
--- a/modules/setting/setting.go
+++ b/modules/setting/setting.go
@@ -117,6 +117,7 @@ var (
 	// Markdown sttings
 	Markdown struct {
 		EnableHardLineBreak bool
+		CustomURLSchemes    []string `ini:"CUSTOM_URL_SCHEMES"`
 	}
 
 	// Picture settings
diff --git a/modules/template/template.go b/modules/template/template.go
index 6099fcc98..d95035c35 100644
--- a/modules/template/template.go
+++ b/modules/template/template.go
@@ -105,7 +105,7 @@ func Safe(raw string) template.HTML {
 }
 
 func Str2html(raw string) template.HTML {
-	return template.HTML(base.Sanitizer.Sanitize(raw))
+	return template.HTML(base.BuildSanitizer().Sanitize(raw))
 }
 
 func Range(l int) []int {