Clarify upgrade steps

doc/update/5.0-to-5.1.md

 # From 5.0 to 5.1
 
 ## Warning
-GitLab 5.1 is affected by critical security vulnerability CVE-2013-4490. Please update to GitLab 5.4 immediately.
+GitLab 5.1 is affected by critical security vulnerability CVE-2013-4490. Please [update to GitLab 5.4 immediately](5.1-to-5.4.md).
 
 ## Release notes:
 

doc/update/5.1-to-6.0.md

 # From 5.1 to 6.0
 
 ## Warning
-GitLab 6.0 is affected by critical security vulnerabilities CVE-2013-4490 and CVE-2013-4489. Please update to GitLab 6.2 or newer immediately.
+GitLab 6.0 is affected by critical security vulnerabilities CVE-2013-4490 and CVE-2013-4489. Please [update to GitLab 6.2 immediately](6.0-to-6.2.md).
 
 ### Deprecations
 

doc/update/5.4-to-6.0.md

 # From 5.4 to 6.0
 
 ## Warning
-GitLab 6.0 is affected by critical security vulnerabilities CVE-2013-4490 and CVE-2013-4489. Please update to GitLab 6.2 or newer immediately.
+GitLab 6.0 is affected by critical security vulnerabilities CVE-2013-4490 and CVE-2013-4489. Please [update to GitLab 6.2 immediately](6.0-to-6.2.md).
 
 ### Deprecations
 

doc/update/6.0-to-6.1.md

 # From 6.0 to 6.1
 
 ## Warning
-GitLab 6.1 is affected by critical security vulnerabilities CVE-2013-4490 and CVE-2013-4489. Please [update straight to 6.2](6.0-to-6.2.md).
+GitLab 6.1 is affected by critical security vulnerabilities CVE-2013-4490 and CVE-2013-4489. Please [update to GitLab 6.2 directly](6.0-to-6.2.md).
 
 # In 6.1 we remove a lot of deprecated code.
 # You should update to 6.0 before installing 6.1 so all the necessary conversions are run.