diff --git a/connector/saml/saml.go b/connector/saml/saml.go
index 29f5dd98..08ff6cbc 100644
--- a/connector/saml/saml.go
+++ b/connector/saml/saml.go
@@ -7,7 +7,6 @@ import (
 	"encoding/base64"
 	"encoding/pem"
 	"encoding/xml"
-	"errors"
 	"fmt"
 	"io/ioutil"
 	"strings"
@@ -15,6 +14,8 @@ import (
 	"time"
 
 	"github.com/beevik/etree"
+	xrv "github.com/mattermost/xml-roundtrip-validator"
+	"github.com/pkg/errors"
 	dsig "github.com/russellhaering/goxmldsig"
 	"github.com/russellhaering/goxmldsig/etreeutils"
 
@@ -287,6 +288,7 @@ func (p *provider) POSTData(s connector.Scopes, id string) (action, value string
 //
 // The steps taken are:
 //
+// * Validate XML document does not contain malicious inputs.
 // * Verify signature on XML document (or verify sig on assertion elements).
 // * Verify various parts of the Assertion element. Conditions, audience, etc.
 // * Map the Assertion's attribute elements to user info.
@@ -297,6 +299,11 @@ func (p *provider) HandlePOST(s connector.Scopes, samlResponse, inResponseTo str
 		return ident, fmt.Errorf("decode response: %v", err)
 	}
 
+	byteReader := bytes.NewReader(rawResp)
+	if xrvErr := xrv.Validate(byteReader); xrvErr != nil {
+		return ident, errors.Wrap(xrvErr, "validating XML response")
+	}
+
 	// Root element is allowed to not be signed if the Assertion element is.
 	rootElementSigned := true
 	if p.validator != nil {
diff --git a/go.mod b/go.mod
index d92f8fbc..86a1e9c8 100644
--- a/go.mod
+++ b/go.mod
@@ -23,7 +23,9 @@ require (
 	github.com/konsorten/go-windows-terminal-sequences v1.0.2 // indirect
 	github.com/kylelemons/godebug v1.1.0
 	github.com/lib/pq v1.3.0
+	github.com/mattermost/xml-roundtrip-validator v0.0.0-20201204154048-1a8688af4cf1
 	github.com/mattn/go-sqlite3 v1.11.0
+	github.com/pkg/errors v0.9.1
 	github.com/pquerna/cachecontrol v0.0.0-20180517163645-1555304b9b35 // indirect
 	github.com/prometheus/client_golang v1.4.0
 	github.com/russellhaering/goxmldsig v1.1.0
diff --git a/go.sum b/go.sum
index 2ce312e9..ada7c048 100644
--- a/go.sum
+++ b/go.sum
@@ -186,6 +186,8 @@ github.com/kylelemons/godebug v1.1.0/go.mod h1:9/0rRGxNHcop5bhtWyNeEfOS8JIWk580+
 github.com/lib/pq v1.3.0 h1:/qkRGz8zljWiDcFvgpwUpwIAPu3r07TDvs3Rws+o/pU=
 github.com/lib/pq v1.3.0/go.mod h1:5WUZQaWbwv1U+lTReE5YruASi9Al49XbQIvNi/34Woo=
 github.com/magiconair/properties v1.8.0/go.mod h1:PppfXfuXeibc/6YijjN8zIbojt8czPbwD3XqdrwzmxQ=
+github.com/mattermost/xml-roundtrip-validator v0.0.0-20201204154048-1a8688af4cf1 h1:D2uMrH5NnWgU7JdjiWjOg/n31gbPH6I0D3IbCrqVVYE=
+github.com/mattermost/xml-roundtrip-validator v0.0.0-20201204154048-1a8688af4cf1/go.mod h1:qccnGMcpgwcNaBnxqpJpWWUiPNr5H3O8eDgGV9gT5To=
 github.com/mattn/go-colorable v0.0.9/go.mod h1:9vuHe8Xs5qXnSaW/c/ABM9alt+Vo+STaOChaDxuIBZU=
 github.com/mattn/go-isatty v0.0.4/go.mod h1:M+lRXTBqGeGNdLjl/ufCoiOlB5xdOkqRJdNxMWT7Zi4=
 github.com/mattn/go-runewidth v0.0.2/go.mod h1:LwmH8dsx7+W8Uxz3IHJYH5QSwggIsqBzpuz5H//U1FU=
@@ -226,6 +228,8 @@ github.com/pelletier/go-toml v1.2.0/go.mod h1:5z9KED0ma1S8pY6P1sdut58dfprrGBbd/9
 github.com/pkg/errors v0.8.0/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pkg/errors v0.8.1 h1:iURUrRGxPUNPdy5/HRSm+Yj6okJ6UtLINN0Q9M4+h3I=
 github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/pquerna/cachecontrol v0.0.0-20180517163645-1555304b9b35 h1:J9b7z+QKAmPf4YLrFg6oQUotqHQeUNWwkvo7jZp1GLU=